DEV: Add gitpod files
xref #47790

1. I split the Docker file into 2 Dockers
2. The base Docker includes the pandas environment, and has a new way to run Mamba in Docker, and builds on my machine (M1 mac). 
3. The `gitpod.docker` copies the base docker, which will speed things up for any Gitpod user, and includes a shallow clone of the repository (more speed). 
4. The workspace file defines some nice VS Code features, and the caches for C, C++, and the creation of `.profile` and `.bashrc`. Some things in there are finicky to order of operations (also in relation to the GitHub action which is coming in the next PR), so I recommend avoiding rearranging that file 😉 
5. I added the Gitpod files in a new library, currently under `root` because there isn't a `tools` library. Maybe in the future, we can discuss renaming `scripts` to `tools` to avoid adding another folder? I don't have a strong opinion on this, I just felt awkward about adding a folder there.

Sidenote: I'm going on a few days vacation, and will be back to test the actions next week so I made this a draft PR for now. If someone with docker/actions experience wants to leave a quick review—awesome. When I'm back, I will be testing it with my private account until I can access a pandas docker hub account.

CC @jorisvandenbossche @mroeschke 
This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. I updated the docker files after local testing. The resulting images are on:
https://hub.docker.com/r/pythonpandas/pandas-dev
https://hub.docker.com/r/pythonpandas/pandas-gitpod

I tried to optimize using micromamba for a while, but couldn't make it work yet. For now, I prefer to have a working gitpod for the upcoming sprints. I am happy to give this another try at a later point in time.  I am planning to merge this, so that people can test it in practice and get some experience with it. 

We can consolidate/improve the docker files in subsequent PRs (eg https://github.com/pandas-dev/pandas/pull/48108)