Add prettier config and format files (#319)

Reviewed-on: https://codeberg.org/Codeberg/pages-server/pulls/319
Reviewed-by: crapStone <codeberg@crapstone.dev>
Co-authored-by: pat-s <patrick.schratz@gmail.com>
Co-committed-by: pat-s <patrick.schratz@gmail.com>

.prettierrc.json

@@ -0,0 +1,8 @@
+{
+  "semi": true,
+  "trailingComma": "all",
+  "singleQuote": true,
+  "printWidth": 120,
+  "tabWidth": 2,
+  "endOfLine": "lf"
+}