docs: add Bun installation instructions to README

[vivekkoya]

Description

Types of changes

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Documentation Update (if none of the other choices apply)
• Others (any other types not listed above)

Checklist

• I have read the Contributing Guide
• I have added the necessary documentation (if appropriate)
• Breaking Change (fix or feature that would cause existing functionality to not work as expected)

Further comments

Successfully built site with bun.

Related Issue

Closes: #

[satnaing]

Thanks for your contribution.