Remove Makefile from all intree extensions (#1312)

* Remove Makefile from all intree extensions

- Makefiles are not really common (rightly so) in JS projects and script
  entries in the package.json are good enough and what they're there
  for.

- Move to using yarn for installing dependencies and running scripts as
  that is what we mostly use for the rest of the project.

- Move from using make syntax to a dedicated script for building and
  testing extensions.

- add jest as extension devDep, go back to using makefile foreach syntax

- add correct exit code

- add yarn check call to install-deps

- add yarn invokation to find deps

Signed-off-by: Sebastian Malton <sebastian@malton.name>

extensions/support-page/Makefile

@@ -1,8 +0,0 @@
-install-deps:
-	yarn install
-
-build: install-deps
-	yarn run build
-
-test:
-	yarn run test

extensions/support-page/package.json

@@ -7,7 +7,7 @@
   "scripts": {
     "build": "webpack -p",
     "dev": "webpack --watch",
-    "test": "echo NO TESTS"
+    "test": "jest --passWithNoTests --env=jsdom src $@"
   },
   "dependencies": {},
   "devDependencies": {
@@ -16,6 +16,7 @@
     "@types/react-router": "^5.1.8",
     "@types/webpack": "^4.41.17",
     "css-loader": "^5.0.0",
+    "jest": "^26.6.3",
     "mobx": "^5.15.5",
     "react": "^16.13.1",
     "sass-loader": "^10.0.4",