[ci skip] New package: electron39. Switch electron rev. deps. to v39.

[JkktBkkt]

Testing the changes

• I tested the changes in this PR: YES — vscode, element-desktop
• briefly — wire-desktop (opens, loads the default page, but I don't really have a means of using it the intended way)

New package

• This new package conforms to the package requirements: YES

Local build testing

• I built this PR locally for my native architecture, x86_64
• I built this PR locally for these architectures (if supported. mark crossbuilds):
  • x86_64-musl (not used the packages with it)

Keeps v35 in current state, though it FTBFS and would probably make sense to remove if this is merged.

cc: @Duncaen as maintainer of electron35 and chromium (which are what I based off of and where I honestly lifted most, if not all, patches from, respectively)