Closes 120 - Replace metacore with metadata

[vedhav]

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Changes Description

1. Replaces the metacore with metadata across all the xportr functions
2. Provide deprecation message for the users
3. Set up deprecation badges for future deprecation by running usethis::use_lifecycle()

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[bms63]

Looking good! Just a few minor comments

[bms63]

Is it possible to drop the docs folder or merge in Andre's removal of docs. Looks like the link checker is falling over from the docs as well as the merge conflicts

[elimillera]

LGTM