v1.5.6-rc.1

Full Changelog

• Update Lithuanian language name
  #11599
• Enable more languages
  #11592
• Fix Docker build for develop and publish a /version file
  #11588
• Remove unused translations
  #11540
• Update from Weblate
  #11591
• Update riot.im enable_presence_by_hs_url for new matrix.org client URL
  #11565
• Remove mention of vector.im as default identity server on mobile guide
  #11544
• Clean up and standardise app config
  #11549
• make it clear that seshat requires electron-build-env (at least on macOS)
  #11527
• Add postcss-easings
  #11521
• ElectronPlatform: Add support for a event index using Seshat.
  #11125
• Sign all of the Windows executable files
  #11516
• Clarify that cross-signing is in development
  #11493
• get rid of bluebird
  #11301
• Update from Weblate
  #11488
• Add note in README about self-hosted riot installs requiring custom caching
  headers
  #8702
• De-dup theming code
  #11445
• Add eslint-plugin-jest because we inherit js-sdk's eslintrc and it wants
  #11448