Convert all *_html.js files to typescript

* Rename all files with the following commands:
  find . -name *_html.js -exec sh -c \
   'dirn=`dirname {}`;bn=`basename {} .js`; git mv {} $dirn/$bn.ts' \;

* Replace in all *_html.ts files
    import {html} from '@polymer/polymer/lib/utils/html-tag.js';
  with
    import {html} from '@polymer/polymer/lib/utils/html-tag';

* Update manually import path in
  gr-hovercard-account_html.ts

* Convert manually gr-hovercard-shared-style.js to .ts

Change-Id: I83102311c70740586514b6f32d03328e2a59c3ec
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
new file mode 100644
index 0000000..40f6a32
--- /dev/null
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import {html} from '@polymer/polymer/lib/utils/html-tag';
+
+export const htmlTemplate = html`
+  <style include="shared-styles">
+    :host {
+      /* Used to remove horizontal whitespace between the icons. */
+      display: flex;
+    }
+    gr-button.selected iron-icon {
+      color: var(--link-color);
+    }
+    iron-icon {
+      height: 1.3rem;
+      width: 1.3rem;
+    }
+  </style>
+  <gr-button
+    id="sideBySideBtn"
+    link=""
+    has-tooltip=""
+    class$="[[_computeSelectedClass(mode, _VIEW_MODES.SIDE_BY_SIDE)]]"
+    title="Side-by-side diff"
+    on-click="_handleSideBySideTap"
+  >
+    <iron-icon icon="gr-icons:side-by-side"></iron-icon>
+  </gr-button>
+  <gr-button
+    id="unifiedBtn"
+    link=""
+    has-tooltip=""
+    title="Unified diff"
+    class$="[[_computeSelectedClass(mode, _VIEW_MODES.UNIFIED)]]"
+    on-click="_handleUnifiedTap"
+  >
+    <iron-icon icon="gr-icons:unified"></iron-icon>
+  </gr-button>
+  <gr-rest-api-interface id="restAPI"></gr-rest-api-interface>
+`;