AngularJS is in LTS mode

We are no longer accepting changes that are not critical bug fixes into this project.
Seehttps://blog.angular.io/stable-angularjs-and-long-term-support-7e077635ee9c for more detail.

Does this PR fix a regression since 1.7.0, a security flaw, or a problem caused by a new browser version?
Yes

What is the current behavior? (You can also link to an open issue here)

• from:483 vulnerabilities found - 273 Low | 38 Moderate | 168 High | 4 Critical
• NodeJS v12 is used

What is the new behavior (if this is a feature change)?

• to: 389 vulnerabilities found - 259 Low | 28 Moderate | 98 High | 4 Critical
• NodeJS LTS v14 is used, the same version as the other Angular repos.

Does this PR introduce a breaking change?
No

Please check if the PR fulfills these requirements

• The commit message follows ourguidelines
• Fix/Feature:Docs have been added/updated
• Fix/Feature: Tests have been added; existing tests pass

Other information:

• This doesn't fix audit issues with the Firebase functions. I plan to do that in a separate PR.
• This doesn't fix all audit issues as I wanted to keep this to a smaller batch as I anticipate future fixes to have more widely breaking changes. This batch is lower risk.
• I tested doc gen and rendering, commit log generation, and building manually in addition to the CI tests.