build: support NodeJS v12 and v14. release script updates.

[Splaktar]

PR Checklist

Please check that your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Build related changes
[x] CI related changes
[x] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

• NodeJS v12 and v14 are not supported as gulp tasks fail due to ReferenceError: primordials is not defined in node
• the release script doesn't update package-lock.json which causes future PRs to awkwardly need to include this change
• none of the docs site snapshots or releases are tagged
• the version number in the commit message and the tags don't match

Issue Number:
Relates to #11844

What is the new behavior?

• add support for NodeJS v12 and v14
• release script updates version in package-lock.json
• remove unused release.sh script
• start tagging docs snapshots and releases
• use more consistent release commit messages and git commands
• improve release script log messages

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

This leverages the approach described in https://stackoverflow.com/a/58394828/633107.

[Splaktar]

@oliversalzburg you should be pretty happy about this change. I'd love to get your feedback on it.

[oliversalzburg]

That looks fantastic! I wish I had known about this before I rewrote our own toolchain to use gulp@4...

[jelbourn]

LGTM