## Issue being fixed or feature implemented
Make Dash on Docker Hub easier to find, a search on `dash` there does
not provide the result.
## What was done?
Improved Docker documentation in `contrib/containers/README.md`
## How Has This Been Tested?
n/a
## Breaking Changes
n/a
## Checklist:
_Go over all the following points, and put an `x` in all the boxes that
apply._
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [x] I have made corresponding changes to the documentation
- [ ] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_
