feat(input): add animation to color change (#10079)

* feat(input): add animation to color change

- add animation to color change when clicking inside an `md-input` field
- previous behaviour was an instant color change
  - which doesn't harmonize with material design guidelines
- use variables for duration and curve of transition

Co-authored-by: Michael Prentice <splaktar@gmail.com>

CHANGELOG.md

@@ -4789,4 +4789,4 @@ Additionally, accessibility support is added to material-button, material-checkb
 * **material-switch:** add switch component ([4975c743](https://github.com/angular/material/commit/4975c7432b814c1e401a48c8e5601ec7a30fa477), closes [#80](https://github.com/angular/material/issues/80))
 * **slider:** add full-featured slider component ([5ea4dbc2](https://github.com/angular/material/commit/5ea4dbc2cbb778884bb164d91fcf9b6262987e52), closes [#260](https://github.com/angular/material/issues/260), [#31](https://github.com/angular/material/issues/31))
 * **switch:** add focus styles ([8878ca7a](https://github.com/angular/material/commit/8878ca7aed861ac4c667cc96de61b8c2e09f9bac))
-* **tabs:** improvements to pagination, disabled tabs, and tab navigation. ([b4244bf3](https://github.com/angular/material/commit/b4244bf3a2d9b97c78361fd0b0189919a710e394))
+* **tabs:** improvements to pagination, disabled tabs, and tab navigation. ([b4244bf3](https://github.com/angular/material/commit/b4244bf3a2d9b97c78361fd0b0189919a710e394))

src/components/input/input.scss

@@ -155,6 +155,7 @@ md-input-container {
     -ms-flex-preferred-size: $input-line-height; //IE fix
     border-radius: 0;
     border-style: solid; // Firefox fix
+    transition: border-color $swift-ease-out-duration $swift-ease-out-timing-function;
 
     // Fix number inputs in Firefox to be full-width
     width: 100%;