free_schema 1.0.0-alpha2

Second alpha. Adds default Schema.org trees per bundle.

### New features

- **Default tree per bundle** (#3632333): content types, vocabularies and
media types get a "Free Schema.org" section in their edit form, with the
same tree editor. The default is printed for every entity of the bundle
without a tree of its own, with tokens replaced by that entity's values,
and replaces any other JSON-LD of the page. The bundle does not need a
Free Schema.org field.
- Defaults are stored as the `free_schema.tree` third-party setting of the
bundle: exported with its configuration and translatable with
Configuration Translation (the entity's language is used).
- New restricted permission: "Administer the default free Schema.org trees
of bundles".
- The field widget shows the inherited bundle default as a read-only
preview while the field is empty.
- New "Clear tree" button in the editor, with a reminder to save the form.

### API changes

- `JsonLdBuilder::__construct()` now takes the entity type manager and the
language manager; the optional token entity mapper moved to the last
argument. Code that extends or instantiates the class directly must be
updated.
- The editor form element moved from `FreeSchemaTreeWidget` to the new
`free_schema.tree_editor` service.

### Upgrade notes

- Rebuild caches after updating (`drush cr` or `drush updb`).
- Grant the new permission to the roles that should edit bundle defaults.
- Import the updated Spanish translations if you use them.