Add inline SVG icons for UI and theme picker

This commit introduces a new PHP file `icons.php` that defines a set of inline SVG icons to replace the Bootstrap Icons webfont. The icons include common UI elements such as calendar, clock, folder, and tag, as well as theme picker icons like sun, moon, snow, droplet, cup, and half. The SVGs are designed to scale with existing font-size rules and are accessible via the `blowdit_icon` function. Additionally, a mapping function `blowdit_theme_icon` is provided to associate theme keys with their corresponding icon names.

css/hljs/github-dark.min.css

@@ -0,0 +1,10 @@
+pre code.hljs{display:block;overflow-x:auto;padding:1em}code.hljs{padding:3px 5px}/*!
+  Theme: GitHub Dark
+  Description: Dark theme as seen on github.com
+  Author: github.com
+  Maintainer: @Hirse
+  Updated: 2021-05-15
+
+  Outdated base version: https://github.com/primer/github-syntax-dark
+  Current colors taken from GitHub's CSS
+*/.hljs{color:#c9d1d9;background:#0d1117}.hljs-doctag,.hljs-keyword,.hljs-meta .hljs-keyword,.hljs-template-tag,.hljs-template-variable,.hljs-type,.hljs-variable.language_{color:#ff7b72}.hljs-title,.hljs-title.class_,.hljs-title.class_.inherited__,.hljs-title.function_{color:#d2a8ff}.hljs-attr,.hljs-attribute,.hljs-literal,.hljs-meta,.hljs-number,.hljs-operator,.hljs-selector-attr,.hljs-selector-class,.hljs-selector-id,.hljs-variable{color:#79c0ff}.hljs-meta .hljs-string,.hljs-regexp,.hljs-string{color:#a5d6ff}.hljs-built_in,.hljs-symbol{color:#ffa657}.hljs-code,.hljs-comment,.hljs-formula{color:#8b949e}.hljs-name,.hljs-quote,.hljs-selector-pseudo,.hljs-selector-tag{color:#7ee787}.hljs-subst{color:#c9d1d9}.hljs-section{color:#1f6feb;font-weight:700}.hljs-bullet{color:#f2cc60}.hljs-emphasis{color:#c9d1d9;font-style:italic}.hljs-strong{color:#c9d1d9;font-weight:700}.hljs-addition{color:#aff5b4;background-color:#033a16}.hljs-deletion{color:#ffdcd7;background-color:#67060c}

css/hljs/github.min.css

@@ -0,0 +1,10 @@
+pre code.hljs{display:block;overflow-x:auto;padding:1em}code.hljs{padding:3px 5px}/*!
+  Theme: GitHub
+  Description: Light theme as seen on github.com
+  Author: github.com
+  Maintainer: @Hirse
+  Updated: 2021-05-15
+
+  Outdated base version: https://github.com/primer/github-syntax-light
+  Current colors taken from GitHub's CSS
+*/.hljs{color:#24292e;background:#fff}.hljs-doctag,.hljs-keyword,.hljs-meta .hljs-keyword,.hljs-template-tag,.hljs-template-variable,.hljs-type,.hljs-variable.language_{color:#d73a49}.hljs-title,.hljs-title.class_,.hljs-title.class_.inherited__,.hljs-title.function_{color:#6f42c1}.hljs-attr,.hljs-attribute,.hljs-literal,.hljs-meta,.hljs-number,.hljs-operator,.hljs-selector-attr,.hljs-selector-class,.hljs-selector-id,.hljs-variable{color:#005cc5}.hljs-meta .hljs-string,.hljs-regexp,.hljs-string{color:#032f62}.hljs-built_in,.hljs-symbol{color:#e36209}.hljs-code,.hljs-comment,.hljs-formula{color:#6a737d}.hljs-name,.hljs-quote,.hljs-selector-pseudo,.hljs-selector-tag{color:#22863a}.hljs-subst{color:#24292e}.hljs-section{color:#005cc5;font-weight:700}.hljs-bullet{color:#735c0f}.hljs-emphasis{color:#24292e;font-style:italic}.hljs-strong{color:#24292e;font-weight:700}.hljs-addition{color:#22863a;background-color:#f0fff4}.hljs-deletion{color:#b31d28;background-color:#ffeef0}

css/style.css

@@ -502,7 +502,8 @@ blockquote {
 	color: var(--chrome-text-hover) !important;
 }
 
-.navbar .nav-link .bi {
+.navbar .nav-link .bi,
+.navbar .nav-link .bd-icon {
 	font-size: 1.15rem;
 	margin-right: 0;
 	vertical-align: -0.05em;
@@ -543,7 +544,8 @@ img.nav-svg-icon {
 	color: #ffffff !important;
 }
 
-.theme-toggle .bi {
+.theme-toggle .bi,
+.theme-toggle .bd-icon {
 	font-size: 1.1rem;
 	margin-right: 0;
 }
@@ -797,7 +799,8 @@ img.nav-svg-icon {
 	white-space: nowrap;
 }
 
-.post-list-meta .bi {
+.post-list-meta .bi,
+.post-list-meta .bd-icon {
 	margin-right: 0.25rem;
 }
 
@@ -865,7 +868,8 @@ img.nav-svg-icon {
 	align-items: center;
 }
 
-.metadata i {
+.metadata i,
+.metadata .bd-icon {
 	color: var(--text-muted);
 	margin-right: 0.35rem;
 }
@@ -896,12 +900,14 @@ img.nav-svg-icon {
 	text-decoration: none;
 }
 
-.btn-primary-gradient .bi {
+.btn-primary-gradient .bi,
+.btn-primary-gradient .bd-icon {
 	margin-right: 0;
 	transition: transform 0.2s ease;
 }
 
-.btn-primary-gradient:hover .bi {
+.btn-primary-gradient:hover .bi,
+.btn-primary-gradient:hover .bd-icon {
 	transform: translateX(3px);
 }
 
@@ -928,7 +934,8 @@ img.nav-svg-icon {
 	transition: all 0.2s ease;
 }
 
-.taxonomy-badge .bi {
+.taxonomy-badge .bi,
+.taxonomy-badge .bd-icon {
 	margin-right: 0.35rem;
 	font-size: 0.85em;
 }
@@ -1207,10 +1214,18 @@ footer.footer-modern a:hover {
 /* ========================================
    ICON SPACING
    ======================================== */
-.bi {
+.bi,
+.bd-icon {
 	margin-right: 0.4rem;
 }
 
+/* Inline SVG icons: sized to 1em via their width/height attrs, aligned like
+   the old icon font, and never shrink inside flex rows. */
+.bd-icon {
+	vertical-align: -0.125em;
+	flex: 0 0 auto;
+}
+
 /* ========================================
    TABBED CODE BLOCKS  (```tabs fences)
    ======================================== */