add login with OAuth button to login page

webserver/pages/login_page.html

@@ -33,7 +33,10 @@
             <button type="button" class="show_password_toggle closed"></button>
         </div>
     </div>
-    <button type="submit">Login</button>
+    <div id="login_buttons">
+        <button type="submit">Login with password</button>
+        <button type="submit" id="login_with_oauth"><img src="/favicon.ico"/></button>
+    </div>
 </form>
 
 <script src="/static/error/error.js" type="text/javascript"></script>

webserver/static/login_page.css

@@ -33,3 +33,23 @@
     font-size: 1.25rem;
     margin-bottom: 8px;
 }
+
+#login_buttons {
+    display: grid;
+    grid-gap: 5px;
+    grid-template-columns: 1fr 43px;
+}
+
+#login_with_oauth {
+    padding: 0 !important;
+        position: relative;
+}
+
+#login_with_oauth img {
+    position: absolute;
+    width: 30px;
+    height: 30px;
+    top: 50%;
+    left: 50%;
+    transform: translateX(-50%) translateY(-50%);
+}