chore: adapt babel config to v8

Remove deprecated `useSpread` option (always-on in Babel 8) and scope
`@babel/preset-react` to `.tsx` files only via overrides. Babel 8's
`@babel/preset-typescript` no longer passes `isTSX: false` for `.ts`
files, so preset-react's globally-added JSX transform would otherwise
make the parser treat TypeScript generic syntax like `<T = ...>` as
JSX and fail to compile.

Author: Lukas742

packages/main/.babelrc.json

@@ -7,15 +7,21 @@
         "browserslistEnv": "production"
       }
     ],
-    [
-      "@babel/preset-react",
-      {
-        "runtime": "automatic",
-        "useSpread": true
-      }
-    ],
     "@babel/preset-typescript"
   ],
+  "overrides": [
+    {
+      "test": "**/*.tsx",
+      "presets": [
+        [
+          "@babel/preset-react",
+          {
+            "runtime": "automatic"
+          }
+        ]
+      ]
+    }
+  ],
   "env": {
     "ssr": {
       "plugins": [