Support creating a local JupyterLite deployment with git2cpp built from the local repo

[ianthomas23]

This adds a new directory lite-deploy containing eveything required to build the local git2cpp source code as an
Emscripten-forge package and create a local JupyterLite deployment that can run it in a terminal.

There are comprehensive instructions in lite-deploy/README.md. Essentially you create a new micromamba environment containing all the dependencies, use make to build everything and then make serve to serve the web site so that you can view it in a browser. If you change the git2cpp source code you can rebuild what is required using make rebuild.

The intention is that will be useful for developers working on PRs to easily see if their changes work in the JupyterLite terminal or not. I intend follow-on work to use this on demand in CI also, perhaps to deploy to Github Pages.

I will need to make new cockle and/or terminal releases next week so that we are using the latest code there, for example the changes that have added to cockle but not released yet to support identifying if coloured output is supported or not.

[ianthomas23]

This now runs but git init and git clone fail with filesystem permission errors. So it can be used but will not be very useful until I have fixed the permissions errors which presumably needs a change in the libgit2 emscripten-forge recipe.

[ianthomas23]

There is a temporary replacement for this in PR #37 that uses cockle rather than a full JupyterLite terminal, and that works today unlike this.