* Replace Help / About Serpent window background
* Copy new web.whatsapp.com SSUAO from PM to Serpent
* Revert last commit & future-proof whatsapp SSUAO
1. Reverted previous commit as unnecessary. Web.whatsapp.com will work with a FF SSUAO as well as a Chrome one.
2. Changed FF rv for whatsapp.com from 61.0 to 68.0 so whatsapp will consider Basilisk & Serpent "up to date" for a while longer
* Fix file ext. to show "Serpent" wordmark
Style sheet was attempting to load about-wordmark.png but actual file is about-wordmark.svg
* Update about-wordmark.svg
* New royalty-free Help / About background image
Also removes the redundant branding version of app.update.url in Pale Moon that was missed when many prefs were merged back into application preferences
Serpent Help / Submit Feedback option currently links to Pale Moon forum. This is fine for official builds, but for unofficial builds, it invites feedback that the forum doesn't want to deal with. This change redirects Submit Feedback to a topic at msfn.org devoted to unofficial builds of Serpent.