feat: implement dynamic theme loading and detection logic

added styles for ytm

readme.md

@@ -1,5 +1,24 @@
 # Borlander
 
+Borlander is a MV3 browser extension that applies a classic Borland blue/yellow theme globally, with optional site-specific overrides.
+
+## Site-specific themes (automatic)
+
+Any folder under `borlander/sites/<site>/styles.css` is treated as a site theme automatically.
+
+* If the folder name looks like a hostname (e.g. `github.com`), it matches when the current page hostname includes that string.
+* A couple themes are **heuristic-based** (currently `sonarr.local`, `gitea.local`) because they may run on custom domains. Those are defined in `borlander/scripts/generate-themes.mjs`.
+
+The registry lives in `borlander/themes.json` and is loaded by both `content.js` and `popup.js`.
+
+### Regenerate `themes.json`
+
+If you add/remove site themes in `borlander/sites/`, re-generate the registry:
+
+```fish
+node borlander/scripts/generate-themes.mjs
+```
+
 
 #### Monkeytype theme