docs: update readme to include bun install

[Electroid]

Description

Adds bun add bootstrap as an installation option, alongside npm and yarn.

Motivation & Context

Bun is a popular package manager, which is compatible with npm/yarn.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

Screenshot of the README.md rendered on GitHub:

Related issues

[julien-deramond]

Thanks for bringing up Bun as an option! While we aim to be comprehensive in our docs, listing every package manager could become overwhelming.
At the moment, npm, pnpm, and Yarn are widely adopted by popular front-end libraries/frameworks documentations.
What do you think, @mdo, or others in the core team?

[mdo]

I'm fine with it.