feat: merge update-v8 in the project

[targos]

Moving my code from https://github.com/targos/update-v8

I tried to do it with minimal code changes:

• Switched CLI arguments parser to yargs
• Changed the backport command from update-v8 backport --sha=xxx to update-v8 backport xxx because this option has always been mandatory
• Restructured the documentation a bit
• Did not bring all the gypfiles because they were only necessary to do the update to V8 6.6 (and that update landed on Node master)

Fixes: #234

[codecov]

Codecov Report

Merging #235 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #235   +/-   ##
=======================================
  Coverage   88.54%   88.54%           
=======================================
  Files          19       19           
  Lines         707      707           
=======================================
  Hits          626      626           
  Misses         81       81

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[devsnek]

ideally this could move invocation under git-node or ncu instead of having its own name?

[targos]

Sure. git node update-v8 ?

[devsnek]

@targos sgtm ¯\_(ツ)_/¯

[joyeecheung]

May be just git node v8? We could introduce something like git node npm later, if anyone thinks it's appropriate.

[joyeecheung]

Or maybe git node deps v8 although it seems a bit wordy

[targos]

changed to git node v8

[targos]

@nodejs/automation