[NonGNU ELPA] new package: eglot-inactive-regions

[Filippo Argiolas <filippo.argiolas@gmail.com>]

Hi all,

a couple of weeks ago I submitted my clangd-inactive-regions package
NonGNU ELPA inclusion. Previous discussion led to renaming the package
to make it more general, so I am submitting it again.

For whom who missed it, it's a little Eglot extension to visually style
inactive preprocessor branches in c/cpp code in a LSP powered way.

You can find more at:
https://github.com/fargiolas/eglot-inactive-regions

This addresses some of the feedback received last time:

- renamed the package to eglot-inactive-regions so it's not limited to
  clangd support only

- added experimental support for ccls skippedRegions, so the rename
  actually makes sense

- turned it into a global minor mode (thanks Gerd!). Now once the mode
  is active globally it gets automatically enabled in an eglot managed
  buffer when an inactive region notification arrives from the LSP
  server

- moved all the user options to defcustoms

I hope this rename won't cause too much disruption to my users.
I think all the changes are for the best but let me know if I broke
anything in the process.

As always, feedback is very welcome!

Cheers,
Filippo