Generate specific transcript in ci

Allow user to specify the language when generating transcripts via GitLab CI, so that:

• Artifact downloads will only contain the desired language
• CI processing time is sped up

@Deevad In order for artifact downloads to work properly, please go to CI/CD settings and add the following variable:

• Key: lang (needs to be lower-case)
• Value: *

Then I can do some final testing.