Add ability to rename uploaded asset files

Is your feature request related to a problem? Please describe.

Currently, the only way to rename an uploaded asset is to download it, rename it locally, then re-upload it (via the “Replace with a new asset” button (#68)). This is obviously far from ideal. Being able to easily rename asset files is expected functionality.

Describe the solution you’d like

The ability to quickly and easily rename assets.

Bonus

The ability to quickly and easily rename multiple assets via a “bulk rename” feature.

This is now live!

More info here: https://www.datocms.com/docs/general-concepts/media-area#asset-management