build: react 16.x should be using "react" in tsconfig, not "react-jsx…

…". also, throw errors when not importing react

we were warned by ides and ts to not import react. it was caused by this. it also caused components which did not import react, and this is a breaking behavior for react 16 consumers

packages/core/.eslintrc.js

@@ -17,7 +17,7 @@ const commonRules = {
   "no-underscore-dangle": "off",
   "import/prefer-default-export": "off",
   "no-plusplus": "off",
-  "react/react-in-jsx-scope": 0,
+  "react/react-in-jsx-scope": "error",
   "react/no-danger": "error",
   "react/jsx-one-expression-per-line": "off",
   "react/prop-types": 0,

packages/core/tsconfig.base.json

@@ -4,7 +4,7 @@
     "target": "es6",
     "moduleResolution": "node",
     "esModuleInterop": true,
-    "jsx": "react-jsx",
+    "jsx": "react",
     "skipLibCheck": true,
     "noImplicitAny": true,
     "baseUrl": "."