Add in method setting for webhooks

[SludgeGirl]

Some webhooks utilise PUT instead of strictly POST, in order to support them I've added in the ability to specify which method the webhook should allow in order to allow for these cases

Let me know if you want any changes to this, it's my first time touching the project so suggestions are more than welcome

[SludgeGirl]

Sorry for the extra force, after a bit more time to think on it I wasn't quite happy with my handling of getHttpMethod, I'm still quite, getEndpointPath only returns the first instance of the output it finds in the logs, this leads to only finding the first method set.

Due to the promise required outputs() from AwsConstruct I can't just return this.methods.join(', ') nor can I use the stack output due to it only returning the first instance

I'd very happily get your opinion on hows best to handle this

[mnapoli]

Can the method be a single option, instead of an array? I think that would simplify the PR a lot, and would cover most use cases?

[SludgeGirl]

Yep that'd make a lot of sense, I've just got those changes pushed up

[mnapoli]

@fredericbarthelet WDYT?

[SludgeGirl]

@mnapoli Sorry for the nudge but is there anything else I need to do to get this one merged in?

[mnapoli]

I'd like to get @fredericbarthelet's opinion on this. I think this PR makes sense.

In any case we'd need tests to cover the new feature.

[SludgeGirl]

I've rebased everything, added in the changes to the docs and unit tests. Let me know if you want anything further done!

[fredericbarthelet]

Thanks for your contribution @SludgeGirl :) ! Will be releasing a new Lift version right away for you to be able tu use this feature.