Upgrade to latest typescript

Otherwise the build keeps failing for me as tsc won't compile anymore.

Not sure why things work on CI/for asher but I don't think this will
cause any additional issues.

package.json

@@ -56,7 +56,7 @@
     "stylelint": "^13.0.0",
     "stylelint-config-recommended": "^3.0.0",
     "ts-node": "^8.4.1",
-    "typescript": "3.7.2"
+    "typescript": "4.0.2"
   },
   "resolutions": {
     "@types/node": "^12.12.7",

yarn.lock

@@ -7088,10 +7088,10 @@ typedarray@^0.0.6:
   resolved "https://registry.yarnpkg.com/typedarray/-/typedarray-0.0.6.tgz#867ac74e3864187b1d3d47d996a78ec5c8830777"
   integrity sha1-hnrHTjhkGHsdPUfZlqeOxciDB3c=
 
-typescript@3.7.2:
-  version "3.7.2"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.7.2.tgz#27e489b95fa5909445e9fef5ee48d81697ad18fb"
-  integrity sha512-ml7V7JfiN2Xwvcer+XAf2csGO1bPBdRbFCkYBczNZggrBZ9c7G3riSUeJmqEU5uOtXNPMhE3n+R4FA/3YOAWOQ==
+typescript@4.0.2:
+  version "4.0.2"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.0.2.tgz#7ea7c88777c723c681e33bf7988be5d008d05ac2"
+  integrity sha512-e4ERvRV2wb+rRZ/IQeb3jm2VxBsirQLpQhdxplZ2MEzGvDkkMmPglecnNDfSUBivMjP93vRbngYYDQqQ/78bcQ==
 
 uncss@^0.17.2:
   version "0.17.3"