Nextra3 and some Scanner docs.

[zacharyblasczyk]

@jsbroks, I couldn't get this to go away... Not sure if it is is a bug or if it is a webpack thing re hot loading.

@ctrlplane/docs:dev:  ⚠ ../../node_modules/@typescript/vfs/dist/vfs.esm.js
@ctrlplane/docs:dev: Critical dependency: the request of a dependency is an expression
@ctrlplane/docs:dev: 
@ctrlplane/docs:dev: Import trace for requested module:
@ctrlplane/docs:dev: ../../node_modules/@typescript/vfs/dist/vfs.esm.js
@ctrlplane/docs:dev: ../../node_modules/twoslash/dist/index.mjs
@ctrlplane/docs:dev: ../../node_modules/@shikijs/twoslash/dist/index.mjs
@ctrlplane/docs:dev: ../../node_modules/nextra/dist/server/compile.js
@ctrlplane/docs:dev: ../../node_modules/nextra/dist/client/components/playground.js
@ctrlplane/docs:dev: ../../node_modules/nextra/dist/client/components/index.js
@ctrlplane/docs:dev:  ⚠ ../../node_modules/@typescript/vfs/dist/vfs.esm.js

I also added some linting/formatting to MDX.