Refactor Dockerfile

[Gauvino]

• Changed emsdk version to the latest one from 2.0.34 to 3.1.51
• Re-arranged the package
• Added clean command

[Gauvino]

Proof of building

[Gauvino]

@dmitrylyzo does this PR is needed or can be closed ?

The repo is abandoned ?

[dmitrylyzo]

I don't remember where I stopped.
IIRC, updating Emscripten to latest was causing JSO to not work in older browsers (TV).
Moreover, it requires more changes: master...dmitrylyzo:JavascriptSubtitlesOctopus:update-emscripten

The idea was to update this repo to upstream (as clean as possible, but without unnecessary changes).
One of those updates: #46

10.9 has moved to JASSUB, so this repo has become less relevant.

[Gauvino]

I don't remember where I stopped.

IIRC, updating Emscripten to latest was causing JSO to not work in older browsers (TV).

Moreover, it requires more changes: master...dmitrylyzo:JavascriptSubtitlesOctopus:update-

Ok, I didn't see this change.

The idea was to update this repo to upstream (as clean as possible, but without unnecessary changes).

One of those updates: #46

10.9 has moved to JASSUB, so this repo has become less relevant.

So this PR is not needed anymore if this repo is being used this jellyfin switch to jassub