all argument types in methods.ts should be exported

[aoberoi]

Description

the symbol names aren't being exported, so some type information is being lost. for example, here is the type for a method: web.oauth.access: Method<methods.TokenOverridable>. i'd expect to see
web.oauth.access: Method<methods.OAuthAccessArguments>.

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.