* Split existing migration document
* Add some overview on migration recipes
* Review legacy migration docs
* Not a lot of changes to the Fluent-to-Fluent parts, intentionally
The changes to the legacy docs are mostly driven by how much
a particular caveat bugged me. There's surely more to do on that doc.
Differential Revision: https://phabricator.services.mozilla.com/D59320
--HG--
rename : intl/l10n/docs/migrations/index.rst => intl/l10n/docs/migrations/fluent.rst
rename : intl/l10n/docs/migrations/index.rst => intl/l10n/docs/migrations/legacy.rst
rename : intl/l10n/docs/migrations/index.rst => intl/l10n/docs/migrations/localizations.rst
rename : intl/l10n/docs/migrations/index.rst => intl/l10n/docs/migrations/overview.rst
rename : intl/l10n/docs/migrations/index.rst => intl/l10n/docs/migrations/testing.rst
extra : moz-landing-system : lando