lint: add lefthook, prettier, typos

[noahp]

Install from npm, because it's simpler, so use lefthook as the
pre-commit runner (yarn install automatically installs the hooks,
which is somewhat nice too).

I removed the reference to the grammarly vscode extension, since it's
no longer available in the marketplace and the github repo is archived.

[cloudflare-workers-and-pages]

Deploying interrupt with    Cloudflare Pages

Latest commit:	a347d91
Status:	✅  Deploy successful!
Preview URL:	https://2ae16d13.interrupt.pages.dev
Branch Preview URL:	https://noahp-lefthook.interrupt.pages.dev

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[gminn]

Thank you so much for adding this! been wanting it for a while ❤️ Can't wait to open the massive formatting and typos fixing PR 💥

[Copilot]

Pull request overview

This PR adds linting infrastructure to the repository by introducing lefthook as a pre-commit hook runner, prettier for markdown formatting, and typos-rs for spell checking. The PR also removes the deprecated Grammarly VSCode extension configuration and updates documentation to reflect the new setup requirements.

Key Changes:

• Adds lefthook, prettier, and typos-rs as npm dependencies with pre-commit hook configuration
• Removes deprecated Grammarly VSCode extension settings and replaces with prettier configuration
• Updates README with instructions for installing yarn dependencies and running linters

Reviewed changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Adds lockfile with lefthook 1.6.16, prettier 3.3.2, and typos-rs-npm dependencies
package.json	Defines npm scripts for linting and declares project dependencies
lefthook.yml	Configures pre-commit hooks to run prettier and typos on staged markdown files
_typos.toml	Provides configuration file for typos spell checker
.vscode/settings.json	Removes Grammarly settings and configures prettier as the default markdown formatter
.gitignore	Adds node_modules and Yarn 2 specific directories to ignore list
.gitattributes	Adds git attributes configuration for binary lockfile handling
readme.md	Updates documentation with yarn installation instructions and reformats text with line wrapping

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[gminn]

Got this branch building again 💪 I also confirmed that the lefthook prettier and typos checks are working well locally!

The error from build logs was:

➤ YN0070: Migrating from Yarn 1; automatically enabling the compatibility node-modules linker 👍

Changes I made to fix it:

• Use Yarn 3:

yarn set version 3.6.3

• Add nodeLinker: node-modules to .yarnrc.yml to configure yarn 3.

• Finally, reset env and regenerate yarn.lock:

rm -rf node_modules && rm yarn.lock
yarn install