Doc: Add mhchem doc

joplin.code-workspace

@@ -13,6 +13,11 @@
 			"**/_mydocs/EnexSamples/*.enex": true,
 			"**/*.base64": true,
 			"**/*.bundle.js": true,
+			"**/*.ttf": true,
+			"**/*.eot": true,
+			"**/*.woff": true,
+			"**/*.woff2": true,
+			"**/*.ico": true,
 			"**/*.icns": true,
 			"**/*.jar": true,
 			"**/*.map": true,
@@ -57,6 +62,7 @@
 			"ElectronClient/build/": true,
 			"ElectronClient/dist/": true,
 			"node_modules/": true,
+			"docs/images/flags": true,
 			"ReactNativeClient/android/.gradle/": true,
 			"ReactNativeClient/android/.idea/": true,
 			"ReactNativeClient/android/app/build/": true,

readme/markdown.md

@@ -88,7 +88,13 @@ For example:
 
 Here is an example with the Markdown and rendered result side by side:
 
-<img src="https://joplinapp.org/images/Katex.png" height="400px">
+<img src="https://joplinapp.org/images/Katex.png" height="345px">
+
+### Chemical equations
+
+Joplin supports chemical equations via the mhchem plugin for KaTeX. This plugin is automatically enabled if you enable math notation. See the [mhchem documentation](https://mhchem.github.io/MathJax-mhchem/) for the syntax.
+
+<img src="https://joplinapp.org/images/Katex_mhchem.png" height="196px">
 
 ### Checkboxes