Use Oslo, MSW, Bun and ESM

[sergiodxa]

• Use @pilcrowOnPaper's Oslo to implement OAuth2 logic instead of doing it myself (this also brings OAuth2 error handling to the strategy cc @rossipedia)
• Use MSW to mock the /tokens requests
• Use Bun as package manager and test runner
• Output only ESM code
• Allow users to re-authenticate
• Don't use crypto-js anymore
• Support PKCE
• Add support for scopes option
• Bumps minimum Node required version to v18
• Use Biome instead of ESLint and Prettier

[pilcrowOnPaper]

Just as an FYI, Oslo requires the Web Crypto API, including subtle