(test): dogfood tsdx test for internal testing

- now that --config is supported, this is fairly straightforward
  - rootDir had to be added because TSDX defaults use app root, and not
    the directory of the jest.config file

package.json

@@ -25,7 +25,8 @@
     "build": "tsc -p tsconfig.json",
     "lint": "yarn build && yarn lint:post-build",
     "lint:post-build": "node dist/index.js lint src test --ignore-pattern 'test/tests/lint'",
-    "test": "yarn build && jest --config ./test/jest.config.json",
+    "test": "yarn build && yarn test:post-build",
+    "test:post-build": "node dist/index.js test --config ./test/jest.config.json",
     "watch": "chokidar \"./package.json\" \"./src/**/*.ts\" \"node_modules\\@jaredpalmer\\rollup-plugin-preserve-shebang\\dist\\index.js\" -c \"yarn build && echo Success\"",
     "start": "tsc -p tsconfig.json --watch"
   },

test/jest.config.json

@@ -1,5 +1,6 @@
 {
   "testEnvironment": "node",
+  "rootDir": "./test",
   "roots": ["<rootDir>/tests"],
   "collectCoverageFrom": ["**/*.js"],
   "transform": {