documenting for semantic highlighting

Signed-off-by: Yan Zhang <yanzh@microsoft.com>

Author: Eskibear

README.md

@@ -160,6 +160,25 @@ New in 0.60.0:
 * `java.sources.organizeImports.staticStarThreshold`: Specifies the number of static imports added before a star-import declaration is used, default is 99.
 * `java.semanticHighlighting.enabled`: Enable/disable the [semantic highlighting](https://github.com/microsoft/vscode/wiki/Semantic-Highlighting-Overview). Defaults to `true`.
 
+Semantic Highlighting
+===============
+[Semantic Highlighting](https://code.visualstudio.com/updates/v1_43#_typescript-semantic-highlighting) is a new feature enabled since VS Code 1.43. Color themes can now write [rules](https://code.visualstudio.com/updates/v1_44#_theme-support-for-semantic-tokens) to color semantic tokens reported by this extension. If current color theme does not provide any, you can define your own rules in user settings, e.g.
+```json
+"editor.tokenColorCustomizationsExperimental": {
+    "variable":{
+        "foreground": "#9CDCFE" // change color for tokens of type 'variable'
+    },
+    "*.static":{
+        "fontStyle": "italic" // all tokens with modifier 'static' should be of italic style
+    },
+    "*.final":{
+        "fontStyle": "bold" // all tokens with modifier 'final' should be of bold style
+    }
+}
+```
+
+More details in [Semantic Highlighting Wiki Page (Token Styling)](https://github.com/microsoft/vscode/wiki/Semantic-Highlighting-Overview#token-styling).
+
 Troubleshooting
 ===============
 1. Check the status of the language tools on the lower right corner (marked with A on image below).