Replace xitter links with Bluesky (#15988)

[maureenlholland]

If this changeset needs to go into the FXC codebase, please add the WMO and FXC label.

One-line summary

Replaces xitter links with bluesky links and adds bluesky icons

Significant changes and points to review

Issue / Bugzilla link

#15988

Testing

• Footer refresh: http://localhost:8000
• Contribute, Our Mission section: http://localhost:8000/en-US/contribute/
• Careers, bottom section: http://localhost:8000/en-US/careers/
• Newsletter opt out confirmation: http://localhost:8000/en-US/newsletter/opt-out-confirmation/
• Contact, Find us online section: http://localhost:8000/en-US/contact/
• Newsletter updated (L33, set to True to view form): http://localhost:8000/en-US/newsletter/updated/

[janbrasna]

Few questions for consistency:

[janbrasna]

Can both the helpers

bedrock/bedrock/mozorg/templatetags/misc.py

Lines 420 to 425 in 6aafa46

	def mozilla_twitter_url(ctx):
	"""Output a link to Twitter taking locales into account.
	Uses the locale from the current request. Checks to see if we have
	a Twitter account that match this locale, returns the localized account
	url or falls back to the US account url if not.

be removed now, incl. tests?

[maureenlholland]

yes, I was checking if we wanted to repurpose for Bluesky, but will remove as it seems we don't have localised account there yet

[janbrasna]

Sometimes it's here "Bluesky" literally, sometimes {-brand-name-bluesky} reference …

IIUC third party brands should no longer be added to the brand terms, so probably can be used spelled out fully in every single string(?)

[maureenlholland]

will check

[maureenlholland]

Sometimes it's here "Bluesky" literally, sometimes {-brand-name-bluesky} reference

this was a miss on my part, I meant to use the brand name ref consistently, still checking on the brand term standards

[maureenlholland]

As discussed internally, we're not going to include the 3rd party brand in FTL files (unless it's part of a larger sentence, in which case we should use a comment to indicate the words that should not be translated), will put directly in HTML

[wen-2018]

Question: I see some Twitter links for the Nightly templates, ex: /Users/jingwen/Documents/projects/bedrock/bedrock/firefox/templates/firefox/nightly/firstrun.it.html <a href="https://twitter.com/mozilla_fr/">@mozilla_fr sur Twitter</a> , should they be removed too?

[maureenlholland]

@wen-2018 it's a good question. I've asked internally. I think they should be removed eventually but question whether it should be as part of this PR or a separate one to follow up on the less visible links (and share urls).

[wen-2018]

The current changes LGTM! r+
Per the internal discussions, other clean ups can be in a separate PR