fix: Make tailwindcss peer dependency optional

[amannn]

fix: Make tailwindcss peer dependency optional

Description

This makes this plugin easier to consume when it's installed as part of a shared config, in case tailwindcss is not installed by the host.

See also: jest-community/eslint-plugin-jest#970

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Known to work from other plugins.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[amannn]

@francoismassart Any chance you have time for a quick review here?