fix(theme-picker,version-picker): add/improve aria-labels and tooltips

Fixes #671

Author: Splaktar

src/app/shared/theme-picker/theme-picker.html

@@ -1,5 +1,5 @@
-<button mat-icon-button [mat-menu-trigger-for]="themeMenu" matTooltip="Select a theme!"
-        aria-label="Open menu to select a theme">
+<button mat-icon-button [mat-menu-trigger-for]="themeMenu" aria-label="Select a theme"
+        matTooltip="Select a theme for the documentation">
   <mat-icon>format_color_fill</mat-icon>
 </button>
 

src/app/shared/version-picker/version-picker.html

@@ -1,4 +1,5 @@
-<button mat-button [matMenuTriggerFor]="versionPicker">
+<button mat-button [matMenuTriggerFor]="versionPicker" aria-label="Select a version"
+        matTooltip="Select a version of the documentation">
   {{materialVersion}}
   <mat-icon>arrow_drop_down</mat-icon>
 </button>

src/app/shared/version-picker/version-picker.ts

@@ -5,6 +5,7 @@ import {MatButtonModule} from '@angular/material/button';
 import {MatIconModule} from '@angular/material/icon';
 import {MatMenuModule} from '@angular/material/menu';
 import {materialVersion, VersionInfo} from '../version/version';
+import {MatTooltipModule} from '@angular/material/tooltip';
 
 const versionUrl = 'assets/versions.json';
 
@@ -32,7 +33,7 @@ export class VersionPicker {
 }
 
 @NgModule({
-  imports: [MatButtonModule, MatIconModule, MatMenuModule, CommonModule],
+  imports: [MatButtonModule, MatIconModule, MatMenuModule, MatTooltipModule, CommonModule],
   exports: [VersionPicker],
   declarations: [VersionPicker]
 })