[astro add] Support adapters and third party packages (#3854)

* feat: support adapters and third part integrations by keywords

* refactor: add keywords to all official integrations

* docs: add adapter ex to astro add help

* nit: clarify astro add usage

* nit: highlight link

* fix: use process.exit(1) on error

* chore: changeset

* nit: bold integration name

* fix: log install instructions for adapters instead

* nit: change to logAdapterConfigInstructions

* Revert "fix: log install instructions for adapters instead"

This reverts commit 1a459f1.

* feat: add hardcoded adapter export map

* refactor: inline adapter config log

packages/integrations/netlify/package.json

@@ -11,6 +11,7 @@
     "url": "https://github.com/withastro/astro.git",
     "directory": "packages/integrations/netlify"
   },
+  "keywords": ["astro-adapter"],
   "bugs": "https://github.com/withastro/astro/issues",
   "homepage": "https://astro.build",
   "exports": {