Add new file for copy (messaging) guidelines

Update copy guidelines

Fix typo

Add forms to guidelines

Simplify Copy heading

Refine copy page. Add images and table

Fix toc link on Copy page

A customer noted an error/lack of clarity in the LDAP documentation
with the `ldap_search` example. Previously, if taken literally, the
customer may have expected the `$` variables to be automatically
replaced or if they paste the exact `user_filter` contents the
parentheses would have been incorrect. Let's just simply the filter
and use exactly what's in the configuration.

The JSON of the example responses were missing a few `,` and therefor
invalid. This adds them to make those JSONs valid.

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Added ability to put emojis into repository name

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Block out pages needed for ux_guide

Add resources stub to ux_guide home

Fill out principles and basics

Add TOC to basics

Move all of UI guide to new UX guide structure

Add first level structure on ux-guide pages

Add more details to buttons

Add button images. Update link on development

Renamed surfaces to templates. Add tooltip details

Update typography and icons on Basics page

Add images for color. First draft of voice and tone

Delete findings page

Refine pages. Fill out Surfaces pages

Clean up layout on basics, surfaces, features. Add anchorlinks and counts to components

Fill out components page

Add item title and system info block

Fill out Features page

Switch tooltip placement image

It adds a button to the branches page that the user can use to delete
all the branches that are already merged. This can be used to clean up
all the branches that were forgotten to delete while merging MRs.

Fixes #21076.

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It was previously possible for invalid credential errors to go unnoticed
in this task. Users would believe everything was configured correctly and
then sign in would fail with 'invalid credentials'. This adds a specific
bind check, plus catches errors connecting to the server. Also, specs :)

https://gitlab.zendesk.com/agent/tickets/48003

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Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342#note_17981421

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342#note_17981448

[e44da1c] Add Label API expected keys to tests

[ac929c8] Update Label API documentation

Add documentation for the "Only allow merge requests to be merged if all discussions are resolved" feature

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>