Add CDP protocol constants for Lightpanda parity methods

Add missing CDP method constants to `src/cdp/protocol.zig`:
- `Network.deleteCookies`
- `Network.setExtraHTTPHeaders`
- `Network.setCookies`
- `Network.getCookies`
- `Page.printToPDF`
- `Page.stopLoading`
- `DOM.querySelector`
- `DOM.querySelectorAll`
- `DOM.getOuterHTML`

This is a dependency for all other Lightpanda parity endpoints.