docs: fix typos and add missing documentation

[selemondev]

This pull request is intended to do three things namely:

1. Fix typographical errors that are found in the documentation.
2. Add missing documentation about the useDocumentText composable.
3. Fix the code display on the useDocumentText composable usage.

[pkg-pr-new]

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reactive-vscode

pnpm add https://pkg.pr.new/KermanX/reactive-vscode@16

@reactive-vscode/mock

pnpm add https://pkg.pr.new/KermanX/reactive-vscode/@reactive-vscode/mock@16

@reactive-vscode/reactivity

pnpm add https://pkg.pr.new/KermanX/reactive-vscode/@reactive-vscode/reactivity@16

create-reactive-vscode

pnpm add https://pkg.pr.new/KermanX/reactive-vscode/create-reactive-vscode@16

@reactive-vscode/vueuse

pnpm add https://pkg.pr.new/KermanX/reactive-vscode/@reactive-vscode/vueuse@16

@reactive-vscode/metadata

pnpm add https://pkg.pr.new/KermanX/reactive-vscode/@reactive-vscode/metadata@16

commit: 096660a

[kermanx]

Thanks a lot!