Desktop: Fixed KaTeX font issue in exported PDF and HTML (#3089)

* Fixed issue: #3078

* updated comments

* Changed as requested

Author: kowalskidev

ReactNativeClient/lib/joplin-renderer/MdToHtml/rules/katex.js

@@ -17,8 +17,30 @@ katex = mhchemModule(katex);
 function katexStyle() {
 	return [
 		{ name: 'katex.css' },
-		// Note: Katex also requires a number of fonts but they don't need to be specified here
-		// since they will be loaded as needed from the CSS.
+		// Note: Declaring the fonts is not needed for in-app rendering because
+		// they will be loaded automatically from katex.css.
+		// However they must be specified for exporting notes to HTML and PDF,
+		// so that they can be bundled with the other assets.
+		{ name: 'fonts/KaTeX_AMS-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Caligraphic-Bold.woff2' },
+		{ name: 'fonts/KaTeX_Caligraphic-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Fraktur-Bold.woff2' },
+		{ name: 'fonts/KaTeX_Fraktur-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Main-Bold.woff2' },
+		{ name: 'fonts/KaTeX_Main-BoldItalic.woff2' },
+		{ name: 'fonts/KaTeX_Main-Italic.woff2' },
+		{ name: 'fonts/KaTeX_Main-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Math-BoldItalic.woff2' },
+		{ name: 'fonts/KaTeX_Math-Italic.woff2' },
+		{ name: 'fonts/KaTeX_SansSerif-Bold.woff2' },
+		{ name: 'fonts/KaTeX_SansSerif-Italic.woff2' },
+		{ name: 'fonts/KaTeX_SansSerif-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Script-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Size1-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Size2-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Size3-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Size4-Regular.woff2' },
+		{ name: 'fonts/KaTeX_Typewriter-Regular.woff2' },
 	];
 }