Update default and incomplete languages for 10.1

Update the list of languages to be available by default in the platform:

• https://github.com/nuxeo/nuxeo-platform-lang-ext/blob/master/src/main/resources/OSGI-INF/deployment-fragment.xml
• https://github.com/nuxeo/nuxeo-platform-lang-ext/blob/master/src/main/resources/OSGI-INF/login-screen-config.xml

Update the list of incomplete languages to be available in the addon Nuxeo Platform Additional Languages. Update language list on:

• https://github.com/nuxeo/nuxeo-platform-lang-ext-incomplete/blob/master/src/main/resources/OSGI-INF/deployment-fragment.xml
• https://github.com/nuxeo/nuxeo-platform-lang-ext-incomplete/blob/master/src/main/resources/OSGI-INF/login-screen-config.xml
• Usage section of https://connect.nuxeo.com/nuxeo/site/marketplace/package/marketplace-lang-ext-incomplete?version=1.2.0-SNAPSHOT

Update documentation page How to translate the Nuxeo Platform.

List of languages should be known when we feature freeze:
Default languages:

• FR
• DE
• ES
• IT
• JA
• NL
• SV
• + languages that are translated at 95% and approved at 75% in Crowdin.

The languages that don't meet these criteria are "incomplete" languages.