feat(theme): add Theme (#741)

* feat(theme): add Theme

* fix(theme): fix broken type test

* docs(theme): add examples

* docs(theme): add description, update carbon theme link [ci skip]

* docs: pre-wrap type code snippet [ci skip]

tests/Theme.test.svelte

@@ -0,0 +1,24 @@
+<script lang="ts">
+  import { Theme } from "../types";
+  import { CarbonTheme } from "../types/Theme/Theme";
+
+  let theme: CarbonTheme = "g10";
+</script>
+
+<Theme
+  bind:theme
+  persist
+  persistKey="carbon-theme"
+  on:update="{(e) => console.log(e.detail.theme)}"
+  tokens="{{ 'button-primary': 'violet' }}"
+  render="toggle"
+  toggle="{{
+    themes: ['g10', 'g90'],
+    labelA: '',
+    labelB: '',
+  }}"
+  select="{{
+    themes: ['g10', 'g90'],
+    labelText: '',
+  }}"
+/>