Add FigShare/Cyverse links to CX report files for METHImpute analyses

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As title says, the README for METHImput_analyses needs a link to provide CX_report files together with links to the official annotation files for the assemblies we used.

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DOI for coverage files (.cov.gz): 10.5281/zenodo.7323783

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DOI for report files (CX_report.txt): 10.5281/zenodo.7695685

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Linked to #9