(Chore) Improve tsconfig

Makes sure that only TS files are included in the list of files to parse by the compiler

Author: Jan Jaap van Deursen

tsconfig.json

@@ -26,6 +26,6 @@
     "target": "es5",
     "downlevelIteration": true
   },
-  "include": ["src/**/*", "custom.d.ts"],
+  "include": ["src/**/*.ts", "src/**/*.tsx", "custom.d.ts"],
   "exclude": ["node_modules", "build", "src/*.json"]
 }