Cannot access 'Add block' button via keyboard

[Dianne Tennent]

Tested on main in Chromium and Firefox

To test:
1. Go to the Edit view of a page
2. Using the tab key, tab through the page

Expected:
 - Can move tab focus to the 'Add block' button

Actual
 - Skips the 'Add block' button

[Kristina Hoeppner (kris-hoeppner)]

It's because it is a <div> so we can drag it.

[Robert Lyon (robertl-9)]

Need to add a tabindex to it

<div tabindex="0">Tab to me</div>

[Mahara Bot (dev-mahara)]

Patch for "main" branch: https://reviews.mahara.org/c/mahara/+/13074

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/c/mahara/+/13074
Committed: https://git.mahara.org/mahara/mahara/commit/9b684b529213f5774e38e0766833343df3bdc441
Submitter: "Gold <email address hidden>"
Branch: main

commit 9b684b529213f5774e38e0766833343df3bdc441
Author: veronicavarsha <email address hidden>
Date: Fri Aug 19 09:49:18 2022 +1200

Bug 1977892: Added tabindex to add block button

Signed-off-by: veronicavarsha <email address hidden>
Change-Id: Iddc8b0de21e6d23f8cd3c31d706415246af0aed7

[Mahara Bot (dev-mahara)]

Patch for "22.04_DEV" branch: https://reviews.mahara.org/c/mahara/+/13143

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/c/mahara/+/13143
Committed: https://git.mahara.org/mahara/mahara/commit/3f902be5fed5232f89fb9ef46561268323ea70ca
Submitter: "Robert Lyon <email address hidden>"
Branch: 22.04_DEV

commit 3f902be5fed5232f89fb9ef46561268323ea70ca
Author: veronicavarsha <email address hidden>
Date: Fri Aug 19 09:49:18 2022 +1200

Bug 1977892: Added tabindex to add block button

Signed-off-by: veronicavarsha <email address hidden>
Change-Id: Iddc8b0de21e6d23f8cd3c31d706415246af0aed7
(cherry picked from commit 9b684b529213f5774e38e0766833343df3bdc441)