Issue body maximum is 65536 characters

[jrarmstro]

This Action should note that maximum size of an issue body is 65536 characters. Attempting to create an issue larger than this results in:

422 Validation Failed [{Resource:Issue Field:body Code:custom Message:body is too long (maximum is 65536 characters)}]

It probably makes sense to emit a warning and truncate issue bodies which exceed this limit.