LSP: Add option to download the TLAPM/LSP.

[kape1395]

This is related to tlaplus/tlapm#93.

The extension could suggest a user download and install the proper version of the TLAPS/LSP.
We should return to this when the LSP support in TLAPM is merged and released.

[lemmy]

FWIW: TLC could also use the JVM that is bundled as part of TLAPS.