Add variables to interface strings to support more languages

[Aonghuso]

Irish has recently been added as an interface language. However, because Irish has verb subject object word order, some of the translations are awkward or just plain wrong because parts of the string are not parts of the message string.

For example

: src/view/com/notifications/FeedItem.tsx:170

msgid "liked your custom feed" msgstr "a mhol do shainfhotha"

: src/view/com/notifications/FeedItem.tsx:155

msgid "liked your post" msgstr "a mhol do phostáil"

The subject is not part of the the string to be localised.

This leads to "X a mhol do phostáil"

But the idiomatic way to say this would be Mhol X do phostáil.

Using a placeholder for the subject would permit this.

[kscanne]

As one of the contributors to the Irish localization, I can confirm that this is a significant problem. There is no way of rephrasing the translation to make it not completely awkward/ungrammatical.

[quiple]

PRs related to this issue: #3911, #3912, #3948, #4494