Add consistent option description for --database on rails new

[akhilgkrishnan]

Motivation / Background

To clarify the description for the --database option in the Rails new command, we are displaying the available database options separated by a forward slash (/).

[--database=DATABASE]    # Preconfigure for selected database (options: mysql/trilogy/postgresql/sqlite3/oracle/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)

Certainly, for other options such as --javascript, --css, and --asset-pipeline, the description lists their available options separated by commas.

[--asset-pipeline=ASSET_PIPELINE]    # Choose your asset pipeline [options: sprockets (default), propshaft]
[--javascript=JAVASCRIPT]    # Choose JavaScript approach [options: importmap (default), bun, webpack, esbuild, rollup]
[--css=CSS]    # Choose CSS processor [options: tailwind, bootstrap, bulma, postcss, sass] check https://github.com/rails/cssbundling-rails for more options

Detail

This Pull Request updates --database options description with a consistent pattern.

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.