Fix test:watch requiring two saves to actually run the code/test you just changed

Will fix https://github.com/nativefier/nativefier/pull/1204#issuecomment-852155755
See package.json in comments for description

package.json

@@ -84,6 +84,10 @@
     "webpack": "^5.24.4",
     "webpack-cli": "^4.5.0"
   },
+  "jest_COMMENTS": {
+    "testPathIgnorePatterns": "See https://jestjs.io/docs/configuration#testpathignorepatterns-arraystring . We set it to 1. ignore coverage for deps, and 2. be sure we test the compiled JS, which is in `lib`, not `src`",
+    "watchPathIgnorePatterns": "See https://jestjs.io/docs/configuration#watchpathignorepatterns-arraystring . We set it for `jest --watch` (a.k.a. `npm run test:watch`) to trigger only after `tsc --watch` (a.k.a. `npm run build:watch`) completes its incremental compilation. Else, jest will pick up immediately on changes in `src` when TSC is barely running, hence testing not-recompiled-yet code and being super confusing, as 1. your changes won't be taken during this first run, and 2. the *next* run (e.g. after a second 'Save' in your editor) will actually have the new code :D"
+  },
   "jest": {
     "collectCoverage": true,
     "setupFiles": [
@@ -94,6 +98,10 @@
       "/node_modules/",
       "<rootDir>/app/src.*",
       "<rootDir>/src.*"
+    ],
+    "watchPathIgnorePatterns": [
+      "<rootDir>/app/src.*",
+      "<rootDir>/src.*"
     ]
   },
   "prettier": {