refs https://github.com/TryGhost/Ghost/issues/15725
This pull request adds a new configuration option for the Mailgun email
provider that allows the user to set the maximum number of recipients
per email batch via a new config option `bulkEmail.batchSize`
As discussed with the product team we want to enforce kebab-case file names for
all files, with the exception of files which export a single class, in which
case they should be PascalCase and reflect the class which they export.
This will help find classes faster, and should push better naming for them too.
Some files and packages have been excluded from this linting, specifically when
a library or framework depends on the naming of a file for the functionality
e.g. Ember, knex-migrator, adapter-manager
