Create a build_block for micromamba

[borin98]

Hello everyone !

I'm opening this issue just to report that I'm working in a PR that contains a build_block with micromamba. I'm optating to work in this issue becase we use a lot Singularity files that contains micromamba in my workspace. Also, I believe that a build_block with micromamba can make the creation of this containers with mamba more quickly.

I'm drawing inspiration from the building block of Miniconda, since micromamba is similar to this package. Any help will be appreciated.

### Tasks

[samcmill]

Sounds great! Looking forward to it.