Export private interfaces

[JeremyFunk]

When trying to separate code into multiple functions using typescript it is sometimes not possible to define the type of arguments because Galeforce does not export all interfaces. An example:

const match = getMatch(matchId) // MatchDTO from galeforce
for (const p of match.data.info.participants){
    const runeData = getRuneData(p)
    ...
}
...

// Here I can't define the type because the Participant type is not exported.
const getRuneData = (participant: ?): string[] => {
    ...
}

Simply exporting all interfaces would solve this issue.
If you don't want to do this (let's be honest it's a really boring task) but think it is a good idea I can create a PR with the changes.

[JeremyFunk]

See #15