Add URL params to control fonts

This was also a good chance to switch to the semantic font size names used in Compound.

test/initializer-test.ts

@@ -0,0 +1,33 @@
+/*
+Copyright 2022 New Vector Ltd
+
+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 { Initializer } from "../src/initializer";
+
+test("initBeforeReact sets font family from URL param", () => {
+  window.location.hash = "#?font=DejaVu Sans";
+  Initializer.initBeforeReact();
+  expect(
+    getComputedStyle(document.documentElement).getPropertyValue("--font-family")
+  ).toBe('"DejaVu Sans"');
+});
+
+test("initBeforeReact sets font scale from URL param", () => {
+  window.location.hash = "#?fontScale=1.2";
+  Initializer.initBeforeReact();
+  expect(
+    getComputedStyle(document.documentElement).getPropertyValue("--font-scale")
+  ).toBe("1.2");
+});