doc: Add steps for transifex to release process

Document how to update settings on and for the transifex website before
and after branch-off of a new release.

Author: laanwj

doc/release-process.md

@@ -37,6 +37,12 @@ Release Process
   - This update should be reviewed with a reindex-chainstate with assumevalid=0 to catch any defect
      that causes rejection of blocks in the past history.
 - Clear the release notes and move them to the wiki (see "Write the release notes" below).
+- Translations on Transifex
+    - Create [a new resource](https://www.transifex.com/bitcoin/bitcoin/content/) named after the major version with the slug `[bitcoin.qt-translation-<RRR>x]`, where `RRR` is the major branch number padded with zeros. Use `src/qt/locale/bitcoin_en.xlf` to create it.
+    - In the project workflow settings, ensure that [Translation Memory Fill-up](https://docs.transifex.com/translation-memory/enabling-autofill) is enabled and that [Translation Memory Context Matching](https://docs.transifex.com/translation-memory/translation-memory-with-context) is disabled.
+    - Update the Transifex slug in [`.tx/config`](/.tx/config) to the slug of the resource created in the first step. This identifies which resource the translations will be synchronized from.
+    - Make an announcement that translators can start translating for the new version. You can use one of the [previous announcements](https://www.transifex.com/bitcoin/bitcoin/announcements/) as a template.
+    - Change the auto-update URL for the resource to `master`, e.g. `https://raw.githubusercontent.com/bitcoin/bitcoin/master/src/qt/locale/bitcoin_en.xlf`. (Do this only after the previous steps, to prevent an auto-update from interfering.)
 
 #### After branch-off (on master)
 
@@ -46,6 +52,8 @@ Release Process
 
 - Update the versions.
 - Create a pinned meta-issue for testing the release candidate (see [this issue](https://github.com/bitcoin/bitcoin/issues/17079) for an example) and provide a link to it in the release announcements where useful.
+- Translations on Transifex
+    - Change the auto-update URL for the new major version's resource away from `master` and to the branch, e.g. `https://raw.githubusercontent.com/bitcoin/bitcoin/<branch>/src/qt/locale/bitcoin_en.xlf`. Do not forget this or it will keep tracking the translations on master instead, drifting away from the specific major release.
 
 #### Before final release