feat(cli): add the --title option to the serve subcommand

[ZakCodes]

As mentioned in this comment, the --title option was never implemented for the serve subcommand.

Here are my 3 test cases to show that it works:

No title provided

OpenAPI Spec

openapi: 3.0.0
info: {}
  # title: Title omitted from the file
paths: {}

Command

redoc-cli serve spec.yml

Expected title

ReDoc Documentation

Title provided in the file

OpenAPI Spec

openapi: 3.0.0
info:
  title: Title given in the file
paths: {}

Command

redoc-cli serve spec.yml

Expected title

Title given in the file

Title provided to the command

OpenAPI Spec

openapi: 3.0.0
info: {}
  # title: Title omitted from the file
paths: {}

Command

redoc-cli serve spec.yml --title "Title given to the command"

Expected title

Title given to the command

Title provided in the file and to the command

OpenAPI Spec

openapi: 3.0.0
info:
  title: Title given in the file
paths: {}

Command

redoc-cli serve spec.yml --title "Title given to the command"

Expected title

Title given to the command

[RomanHotsiy]

Thanks!