New Trello document loader (#4767)
# Added New Trello loader class and documentation
Simple Loader on top of py-trello wrapper.
With a board name you can pull cards and to do some field parameter
tweaks on load operation.
I included documentation and examples.
Included unit test cases using patch and a fixture for py-trello client
class.
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Co-authored-by: Dev 2049 <dev.dev2049@gmail.com>
