doc: comments for codebase and updated documentation

src/features/DisplayFont/model/store/displayedFontsStore.svelte.ts

@@ -1,5 +1,10 @@
 import { selectedFontsStore } from '$entities/Font';
 
+/**
+ * Store for displayed font samples
+ * - Handles shown text
+ * - Stores selected fonts for display
+ */
 export class DisplayedFontsStore {
     #sampleText = $state('The quick brown fox jumps over the lazy dog');
 

src/features/DisplayFont/ui/FontSampler/FontSampler.svelte

@@ -10,8 +10,17 @@ import {
 import { ContentEditable } from '$shared/ui';
 
 interface Props {
+    /**
+     * Font info
+     */
     font: UnifiedFont;
+    /**
+     * Text to display
+     */
     text: string;
+    /**
+     * Font settings
+     */
     fontSize?: number;
     lineHeight?: number;
     letterSpacing?: number;