chore: Move tailwindcss to devDependency & peerDependency

[xeho91]

Description

Moves tailwindcss to in ./package.json from dependencies to:

• devDependencies - for developing & testing the plugin
• and to peerDependencies, so the projects which use your awesome plugin can install tailwindcss on their own, with a certain version.

The installation instructions in the ./README.md also got updated.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

There is no need for testing this, AFAIK.

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
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[francoismassart]

Thank you for contributing @xeho91 👍