Update README to Document Only Built-in Vim/Neovim Text Objects

[m4xshen]

In README.md (lines 58-59):

• q: Quote (or ', ", ```)
• b: Bracket (or (, {, [, <)

It seems there’s some overlap between built-in Vim/Neovim text objects and plugin-specific ones. For example:

• b and B are built-in text objects (b for ( and B for {),
• [, <, and similar objects are also supported (e.g., di[ or da<), but these are not grouped under b as described in the README.

I understand this grouping might be configured using a plugin. However, since not everyone has the same plugin setup, it might be clearer to document only the built-in text objects and remove references to q, as it is not a built-in text object.

If this suggestion works for you, I’d be happy to open a PR.