Add competing interests table and statement

[agitter]

This is a work in progress. I'll need to check the artifacts to make sure the table renders correctly and will request a review when it works.

Did you add yourself as a contributor if this is your first contribution?

• [x] Yes, I added myself or am already a contributor

Any more details? Derived from https://github.com/greenelab/covid19-review/blob/master/content/70.coi-contribs.md

[agitter]

The competing interests table now renders as expected:

[rasbt]

The above looks good. For consistency. Should we use a period at the end of each description? Probably more of a meta-data update, though.

[agitter]

Good idea @rasbt. I added that in 043c89f.