UI Improvements

## Description
The VEDA team has conducted user interviews and gathered some feedback on the initial prototype of STAC admin: https://github.com/NASA-IMPACT/veda-backend/issues/304. Although this feedback is fairly high level, we could use it to guide certain features for an upcoming STAC-admin release.

Some features requests include:

- Ability to create a new collection with required fields (mandatory) + additional fields. Identify which are required field and which are optional.
- Edit all the fields that are present in a collection/item (not just a subset)
- Ability to apply a change to all collections/all items in a collection or a select list of collections. For example for things like stac-extensions or license or renders.colormap_name
- License field should be a dropdown of all the valid values
- Validation of fields (ex - url provided is valid and returns a 2XX response; if stac-extensions is provided, check the schema validity)

## PI Objective
Objective DS-2: STAC Admin NASA-IMPACT/veda-architecture#454

## Acceptance Criteria

- [ ] UI improvements are available in updated release of STAC Admin