Switches client code from JS to TS

[walmazacn]

Description

Changes proposed in this pull request:

• switches client code from JS to TS

Related issue(s)

Resolves #3791

[ndricimrr]

I think the old ../client/src/luigi-client.js (100+ lines) was used to generate the luigi-client-api.md (1400+ lines) sections.

It seems like documentation.js generates .md file by recursively going into the code, starting with imports (in the strict order they were written), which explains why 1400+ lines of .md.

So if you give it another file with different types of imports and different structure (luigi-client.d.ts) it will completely change how the resulting .md looks like.

I don't think we can ever review that .md file if we completely change the imports, and we'll never know if we missed/lost some docu in the process, so the best bet would be to keep the imports in src/luigi-client.ts exactly the same as luigi-client.js , and push for 'any' typings in there where needed , so don't mess up the docu 🤔 .

I think the luigi-client.d.ts was created with the purpose of having typings for Typescript users because we only had luigi-client**.JS** . We would have wanted to have an auto .d.ts generation at some point to avoid having to maintain a manually written extra .d.ts typings file, so there goes luigi-client.d.ts which might be a bit chaotic because we only wanted to export types not use it for documentation.

Which is why I think luigi-client.d.ts shouldn't be used in this case to generate docu but rather the new luigi-client.ts

[walmazacn]

It seems to be some issue with parsing TS files that comes from documentation lib - according to their changelog it was fixed in version 14.0.2:
https://github.com/documentationjs/documentation/blob/master/CHANGELOG.md#bug-fixes-1

I tested the latest version locally and it can handle TS imports correctly - but unfortunatelly many newlines are removed and output file is unreadable :( Similar issue is already reported:
documentationjs/documentation#1595

I can see some possible solutions here, but none of them is perfect:

1. fork documentation lib from lower version and try to fix TS issue on our own
2. freeze building of documentation file for client until TS issues are fixed - API is not updated so often