feat(input): add ionic theme (#29247)

Issue number: internal

---------

## What is the new behavior?
Adds the initial files for the Ionic input.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

core/src/components/input/input.ionic.scss

@@ -0,0 +1,5 @@
+@import "./input";
+@import "./input.ionic.vars";
+
+// Ionic Input
+// --------------------------------------------------

core/src/components/input/input.ionic.vars.scss

@@ -0,0 +1,4 @@
+
+// Ionic Input
+// --------------------------------------------------
+

core/src/components/input/input.tsx

@@ -28,7 +28,7 @@ import { getCounterText } from './input.utils';
   styleUrls: {
     ios: 'input.ios.scss',
     md: 'input.md.scss',
-    ionic: 'input.md.scss',
+    ionic: 'input.ionic.scss',
   },
   scoped: true,
 })