Add-on Store: replace old user guide "AddonsManager" anchor with "AddonStore". Embed hidden HTML to enable the former to still work

[XLTechie]

Link to issue number:

Implements #14961 (comment)

Summary of the issue:

Even though the Add-ons Manager has been replaced by the Add-on Store, the anchor used for jumping to the appropriate section of the User Guide was still "AddonsManager".
The original intent was to leave it that way, because of links to this section which might exist outside of NV Access's control.

The comment proposed a solution that both changes the anchor to be appropriate to the store, and provides a mechanism for the older anchor to continue to bring readers to the new store chapter.

Description of user facing changes

Readers will be able to reach the Add-on Store chapter of the User Guide via either #AddonStore or #AddonsManager, in the HTML version of the User Guide.

Description of development approach

Because we use Txt2Tags 2.5 instead of 2.6, it is not possible to use the ''' method of including raw HTML, as suggested in the original comment. An alternative method has been used.

1. Renamed the anchor for the chapter "Add-ons and the Add-on Store", from "AddonsManager" to "AddonStore".
2. Changed all links in the User Guide that referenced "#AddonsManager" to "#AddonStore".
3. Added some escaped raw HTML before the "Add-ons and the Add-ons Store" chapter, to enable use of the old anchor. It results in two <a name...> elements--one for the new anchor, and one for the old.
4. Included an HTML comment so future editors will understand what's going on.
5. Modified userGuide.t2tconf to enable inclusion of HTML by converting < to {{, and > to }}. This is done using the T2T procedure outlined here.
6. Added a "Raw HTML inclusion" section to the userGuideStandards.md file.

Testing strategy:

Manual testing that the anchors both work.

Known issues with pull request:

1. The new anchor is currently "AddonStore". Should we switch this to "Addons"? The chapter could reasonably be either, and "#Addons" is shorter.
2. Should we use a T2T comment instead of an HTML comment, on line 2543 of the User Guide (relating to number 4 above)? An HTML comment will show up in the source HTML of the output; a T2T comment won't.

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• Security precautions taken.

[seanbudd]

We're rejecting this. These changes create unnecessary complexity, without any gain.