getInitials: handle more cases

See [#5029]][0].

[0]: https://github.com/signalapp/Signal-Desktop/pull/5029

ts/test-both/util/getInitials_test.ts

@@ -0,0 +1,62 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { getInitials } from '../../util/getInitials';
+
+describe('getInitials', () => {
+  it('returns undefined when passed undefined', () => {
+    assert.isUndefined(getInitials(undefined));
+  });
+
+  it('returns undefined when passed an empty string', () => {
+    assert.isUndefined(getInitials(''));
+  });
+
+  it('returns undefined when passed a string with no letters', () => {
+    assert.isUndefined(getInitials('123 !@#$%'));
+  });
+
+  it('returns the first letter of a name that is one ASCII word', () => {
+    assert.strictEqual(getInitials('Foo'), 'F');
+    assert.strictEqual(getInitials('Bo'), 'B');
+  });
+
+  [
+    'Foo Bar',
+    'foo bar',
+    'F Bar',
+    'Foo B',
+    'FB',
+    'F.B.',
+    '0Foo 1Bar',
+    "Foo B'Ar",
+    'Foo Q Bar',
+    'Foo Q. Bar',
+    'Foo Qux Bar',
+    'Foo "Qux" Bar',
+    'Foo-Qux Bar',
+    'Foo Bar-Qux',
+    "Foo b'Arr",
+  ].forEach(name => {
+    it(`returns 'FB' for '${name}'`, () => {
+      assert.strictEqual(getInitials(name), 'FB');
+    });
+  });
+
+  it('returns initials for languages with non-Latin alphabets', () => {
+    assert.strictEqual(getInitials('Иван Иванов'), 'ИИ');
+    assert.strictEqual(getInitials('山田 太郎'), '山太');
+    assert.strictEqual(getInitials('王五'), '王五');
+  });
+
+  it('returns initials for right-to-left languages', () => {
+    assert.strictEqual(getInitials('فلانة الفلانية'), 'فا');
+    assert.strictEqual(getInitials('ישראלה ישראלי'), 'יי');
+  });
+
+  it('returns initials with diacritical marks', () => {
+    assert.strictEqual(getInitials('Ḟoo Ḅar'), 'ḞḄ');
+  });
+});