feat: Add extension to relative imports/exports in declaration files

[lachlancollins]

Uses the following regex to add .js or .cjs extensions to declaration files:

content = content.replace(
  /^import\s[\w{}*\s,]+from\s['"]\.\/[^.'"]+(?=['"];?$)/gm,
  '$&.js',
)

content = content.replace(
  /^export\s[\w{}*\s,]+from\s['"]\.\/[^.'"]+(?=['"];?$)/gm,
  '$&.js',
)

Added @arethetypeswrong/cli to ensure all module resolutions pass.

Fixes TanStack/router#1087