chore: update .gitignore and tsconfig.json

- I often find myself testing formatting on more than one test file, so now files like `test2.js` in the root are ignored.
- Coverage reports contain JS files. `tsc` should ignore them.

.gitignore

@@ -3,7 +3,7 @@
 /scripts/release/node_modules
 *.log
 /errors
-/test.*
+/test*.*
 /.vscode
 /dist
 /website/node_modules

tsconfig.json

@@ -10,6 +10,7 @@
     "strict": false
   },
   "exclude": [
+    "coverage/",
     // [TBD] JavaScript sources *not* affected by src/language-*:
     "src/main/ast-to-doc.js",
     "src/main/core.js",