George Kalpakas 2af8099fbc fix(docs-infra): use up-to-date URLs in "Contribute" links (and replace deprecated md-button) (#40944)
This commit replaces some outdated URLs in "Contribute" links (on the
"Contribute" page):
- `github.com/angular/material2` --> `github.com/angular/components`
- `github.com/angular/angularfire2` --> `github.com/angular/angularfire`

It also replaces the deprecated `md-button` attribute with `mat-button`.

PR Close #40944
2021-02-26 15:39:29 -08:00
..
2021-02-22 12:37:40 -08:00