add comments

static/js/markdown.js

@@ -3,6 +3,10 @@ const Mode = {
   Dark: 2,
 };
 
+/**
+ * Change the svg color theme based on the mode
+ * @param {Mode} mode
+ */
 const svgChangeTheme = (mode) => {
   for (const item of document.getElementsByTagName("img")) {
     if (!item.src.startsWith("data:image/svg+xml;base64,")) {
@@ -10,12 +14,20 @@ const svgChangeTheme = (mode) => {
       continue;
     }
 
-    /** Convert to grayscale */
+    /**
+     * Convert to grayscale
+     * @param {{r: number, g: number, b: number}} color
+     * @returns Number between 0 and 255
+     */
     const colorToGrayscale = (color) => {
       return 0.3 * color.r + 0.59 * color.g + 0.11 * color.b;
     };
 
-    /** Extract color using canvas2d */
+    /**
+     * Extract color using canvas2d
+     * @param {HTMLImageElement} image Image source
+     * @returns Colors represeting the image
+     */
     const extractColors = (image) => {
       const canvas = document.createElement("canvas");
       canvas.width = image.width;