🔧 Point repo metadata at Gitea; drop redundant .npmignore

The repository.url shipped github.com/tmueller/... but the real remote
is gitea.e1nsnull.de/tmu/..., so the npm page's Repository link 404'd.
Add homepage + bugs, fix the URL, and rename the CONTRIBUTING "GitHub"
reference to the forge. Delete .npmignore: when a package.json `files`
allowlist is present npm never consults .npmignore, so it was dead
weight that would only drift. Add "gitea" to the cspell dictionary.

cspell.json

@@ -18,7 +18,8 @@
         "attw",
         "arethetypeswrong",
         "knip",
-        "tsgolint"
+        "tsgolint",
+        "gitea"
     ],
     "ignorePaths": ["dist", "node_modules", "coverage", "*.svg", ".gitignore"]
 }