* master: (389 commits)
Document "No gems fetched from git repositories" policy [ci skip]
Typos
Small gramatical tweaks
Typos
Added PHP & NPM doc
Use `:empty_project` where possible in request specs
Add caching of droplab ajax requests
Use `:empty_project` where possible in model specs
Revert 3f17f29a
Remove unused js response from refs controller
Add MR id to changelog entry
fixed small mini pipeline graph line glitch
Prevent form to be submitted twice
Fix Error 500 when repositories contain annotated tags pointing to blobs
Fix /explore sorting (trending)
Simplify wording in "adding an image" docs
Remove "official merge window" from CONTRIBUTING.md [ci skip]
Update repository check documentation
Fixed flexbox and wrap issues
Update two_factor_authentication.md
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Add todo toggle event
## What does this MR do?
Adds a custom jQuery event `todo:toggle` to detect when a new todo is added so that the respective todo counters (header navigation and sidebar) can update as needed
## Are there points in the code the reviewer needs to double check?
* I wasn't sure whether each `spec` should be modularized based on the html templates or whether they should be separated based on function. There are some crossovers between the `dashboard_spec` and the `header_spec`.
* The naming conventions for `sidebar` and `right_sidebar` were a little confusing since they were named the opposite in their `specs`. I made a few assumptions and named a few files based on what I thought they should be named. I'd be happy to change it to something else though 😄
## Why was this MR needed?
This resolves an existing issue where the todo count on the sidebar would not update (until refresh) and refactors the existing methods that are used to update the todo counters (header navigation and sidebar)
## What are the relevant issue numbers?
Closes#20140
## Does this MR meet the acceptance criteria?
- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
- [x] Added for this feature/bug
- [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
See merge request !5724
