docs: add license, CI, fix content quality, document rcd provider (#38)

- Add 0BSD LICENSE (matches gogrlx/grlx)
- Add GitHub Actions CI workflow (build + eslint)
- Fix eslint config: add ignores for .astro/dist, add typescript parser deps
- Update README: replace npm boilerplate with bun commands, add badges
- Document rc.d (BSD) service provider alongside systemd
- Update service ingredient to reference provider interface instead of claiming systemd-only
- Fix frontmatter: desc -> description in groups.md and user.md
- Close unclosed :::note directive in ingredients overview
- Fix typo in ingredients overview ('Check them out the list' -> 'Check out the list')
- Update astro 5.17.3 -> 5.18.0

package.json

@@ -16,15 +16,18 @@
     "@fontsource/ibm-plex-sans": "^5.2.8",
     "@fontsource/ibm-plex-serif": "^5.2.7",
     "@tailwindcss/vite": "^4.2.1",
-    "astro": "^5.17.3",
+    "astro": "^5.18.0",
     "sharp": "^0.34.5",
     "tailwindcss": "^4.2.1"
   },
   "devDependencies": {
-    "eslint": "^9.27.0",
+    "@typescript-eslint/parser": "^8.56.1",
+    "astro-eslint-parser": "^1.3.0",
+    "eslint": "^9.39.3",
     "eslint-plugin-astro": "^1.6.0",
     "prettier": "^3.8.1",
     "prettier-plugin-astro": "^0.14.1",
-    "prettier-plugin-tailwindcss": "^0.7.2"
+    "prettier-plugin-tailwindcss": "^0.7.2",
+    "typescript": "^5.9.3"
   }
 }