feat(icon): add utility to mirror icons in RTL

[crisbeto]

Adds the mat-icon-rtl-mirror CSS class that can be used to mirror icons only in an RTL layout.

Fixes #10045.

[jelbourn]

LGTM

In the future I could see making this an input and adding a MAT_ICON_OPTIONS provider like we have for other components, but this is good for now (and could easily be backwards compatible w/ changing it in the future).

[crisbeto]

I wanted to avoid having an input that just toggles a class (I think we've had that discussion before). As for configuring it globally, I didn't do it because not all icons should be mirrored.

[philip-firstorder]

This is simple, efficient and flexible. Solves our problems.
Would be cool if the material icons page can also add a rtl flag in the details for each icon. So we know if it is recommended to mirror it on rtl.
I will open a ticket there for this.

[philip-firstorder]

I found a list of icons that can be mirrored here: http://google.github.io/material-design-icons/#icons-in-rtl

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}