Add list functionality to rich text editor (#9871)

* adds buttons to toggle bulleted and numbered lists on and off
* adds icons for those buttons
* css changes to timeline display
* adds tests for the new buttons, refactors existing tests

src/i18n/strings/en_EN.json

@@ -2135,6 +2135,8 @@
     "Stop recording": "Stop recording",
     "Italic": "Italic",
     "Underline": "Underline",
+    "Bulleted list": "Bulleted list",
+    "Numbered list": "Numbered list",
     "Code": "Code",
     "Link": "Link",
     "Edit link": "Edit link",