Implement synchronous alternative for `IBallchasingAPI` functions.

[TristanPearce]

It would be useful for some use-cases to have sync versions of the async functions.

[TristanPearce]

I see two good ways of doing this:

• As extention methods to the IBallchasingAPI class.
• As default-implemented functions on the IBallchasingAPI interface.

The second option seems better in my opinion. It allows the implementor to change the implementation of the sync and async methods seperatly if it is desired. Otherwise it just blocks until the async method returns.

Example

interface IBallchasingAPI 
{
    // Example async function.
    async Task<Result> GetAsync(string id);

    // Default implementation of the sync function.
    // Can optionally be overridden by the implementor.
    Result Get(string id) => GetAsync(id).GetAwaiter().GetResult();
}