[TASK] Allow theme configuration during frontend start

[paulovmr]

Description

Allow the theme to be passed during the command to serve the frontend.

Acceptance Criteria

The following commands will serve the frontend using Patternfly default theme:

npm run start:dev --theme=default-theme
npm run start:dev:mock --theme=default-theme

The following commands will serve the frontend using Material UI theme (default):

npm run start:dev --theme=mui-theme
npm run start:dev:mock --theme=mui-theme