Add supported metrics md

[noelchen90]

Overview

• Exclude tables when checking markdown line length (markdown-lint MD013 doc) since markdown tables will wrap themselves when too long.
• Add supported_metrics.md in docs

Blocked by

• NA

[pfliu-nlp]

Thanks! @noelchen90 Some metrics are commonly used in summarization, while others are preferably used in machine translation. I made a few edits in the doc, and feel free to check.

[noelchen90]

Thanks @pfliu-nlp, I have updated the table according to the doc now!