these folder are already "excluded" implicitly, since we only include "./src" folder
not sure why, but seems like it doesn't like `[jt]s` – which causes it to skip certain .d.ts files, making tsc fail
this prevents tsc from unnecessarily transpiling the frontend part as well: previously it was transpiled by tsc, but the files got discarded and replaced by the files built by webpack. speeds up tsc command a bit as well: from 14 seconds to ~8 secs
