feat($anchorScroll) Allow $anchorScroll to take a numeric input

[mrLarbi]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Feature

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

Allow $anchorScroll to take a numeric input
Ref #14680

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

$anchorScroll can now take a numeric input :

$anchorScroll(7);

Does this PR introduce a breaking change?

No

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:

Ref #14680

Before the change :

$anchorScroll(7); Does not work

After the change :

$anchorScroll(7); works

[gkalpak]

Thx for the PR 👍
It looks good, but we also need at least one test (to verify the new behavior and guard against future regressions).

_{(Feel free to ping me when you have pushed any changes, so I can take another look.)}

[mrLarbi]

@gkalpak Hi gkalpak !

I've added two unit tests. One to check if $anchorScroll still works with a hash of type string. And another one to test the new behavior. :)

[gkalpak]

LGTM