This is one of many MRs opened in order to improve the overall
internationalisation of the GitLab codebase.

This commit only targets Vanilla JS files.

i18n documentation
https://docs.gitlab.com/ee/development/i18n/externalization.html

Changed the placeholder text of the diff tree filter input

Closes #58339

See merge request gitlab-org/gitlab-ce!28352

Add :registrations_recaptcha feature flag

Closes gitlab-ee#11389

See merge request gitlab-org/gitlab-ce!28296

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

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58339

Allows instance owners to toggle the recaptcha requirement
on the user registration page by feature flag.
Allows GitLab Growth team to measure
reCAPTCHA's impact on registrations.

Part of adding Let's Encrypt certificates for pages domains

Add acme-client gem

Client is being initialized by private key stored in secrets.yml
Let's Encrypt account is being created lazily.
If it's already created, Acme::Client just gets account_kid by
calling new_account method

Make Let's Encrypt client an instance
Wrap order and challenge classes

i18n JS files starting with i

See merge request gitlab-org/gitlab-ce!28010

An instance of i18n which required sprintf was not handled correctly
and has been fixed in this commit.

Further to this, i18n was applied to
  app/assets/javascripts/new_branch_form.js
but needed to be removed as the i18n was too vague.

A note has been made to follow up on this file.