Add accelerator keys for template menus (Write, Forward, Reply, Reply All and Reply to List)

[RealRaven2000]

It is noticeable that the extra step of selecting an action from the new SmartTemplates button when we try to reply or forward using templates is adding some extra mouse work / cognitive load that is especially jarring when doing multiple replies in a short space. As a first measure, we should add keyboard accelerators that work well within the current locale. E.g. (F)orward, (R)eply, Reply to (A)ll and Reply to (L)ist. This will be especially more consistent as all templates also have keyboard shorcuts:

[RealRaven2000]

Below is a fully localized test version. tried to also generate logical / useful accelerator keys for cyrillyic languages. I used the English accelerator keys for Asian locales (japanese and Chinese). Also see #263 for even more improvements in following up.

smartTemplate-fx-4.3pre5.zip

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To install the version above, download the zip file and then drag the file into Thunderbird Add-ons Manager. Do not extract contents, it will not install that way. (Github does not allow xpi files in comments but technically a zip file is the same)

[RealRaven2000]

While working on #263 I realized we also need a shortcut for writing new mails (and accelerator for Write) - here it is:

smartTemplate-fx-4.3pre84.zip

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To install the version above, download the zip file and then drag the file into Thunderbird Add-ons Manager. Do not extract contents, it will not install that way.

[RealRaven2000]

Implemented in 4.3.1 - published 16/10/2023