Add MERS-CoV Nextclade community dataset entry

[jrotieno]

Description of proposed changes

To add a MERS-CoV nextclade dataset for rapid clade assignment.

At present, only able to assign clades (A, B and C) but not lineages (will be added at a later date).

Related issue(s)

Checklist

• Checks pass
• Check if changes affect the resource index JSON revision

[joverlee521]

Thanks for adding your dataset @jrotieno.

Since you specifically mentioned that this is a Nextclade dataset, I want to make sure that you are aware that this PR is only adding a link to view your tree to the https://nextstrain.org/community page. This does not add the dataset to the listed community datasets on https://clades.nextstrain.org/. If you want to submit a Nextclade dataset, please follow the dataset create guide and submit at PR in https://github.com/nextstrain/nextclade_data.