Add a NERDTreeToggleVCS command to the vcs plugin

[willfindlay]

Description of Changes

Added a new command NERDTreeToggleVCS to the vcs plugin that behaves exactly like NERDTreeToggle except attempt to root at VCS root when creating the tree for the first time.

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New Version Info

Author's Instructions

• Derive a new MAJOR.MINOR.PATCH version number. Increment the:
  • MAJOR version when you make incompatible API changes
  • MINOR version when you add functionality in a backwards-compatible manner
  • PATCH version when you make backwards-compatible bug fixes
• Update CHANGELOG.md, following the established pattern.

Collaborator's Instructions

• Review CHANGELOG.md, suggesting a different version number if necessary.
• After merge, tag the merge commit, e.g. git tag -a 3.1.4 -m "v3.1.4" && git push origin --tags

[willfindlay]

Thanks for the review @PhilRunninger. I've made your requested changes.

[PhilRunninger]

Looks good. Thanks for following the PR template's instructions.