Add devcontainer

[yousefmoazzam]

The idea is to provide a development environment for httomo that is easily reproducible, for both testing and development purposes.

Containers are one such tool that provide such reproducibility, and modern IDEs such as VSCode and PyCharm support the ability to develop inside a container, while still being able to use all the features that the IDE provides when developing normally/outside of a container (such as autocompletion, debugging, Ctrl-click to jump to a definition, etc).

• add Dockerfile for base container image with all deps of httomo, httomolib, and httomolibgpu installed
• add basic config for dev container image
• add support for VSCode
• add support for PyCharm
• add documentation on how to use the dev container

[yousefmoazzam]

Adding support for PyCharm has been put on hold for the moment, as the Dev Container plugin by JetBrains is unfortunately only available for the professional edition of PyCharm (ie, the paid edition of PyCharm).

There does appear to be some information in the PyCharm docs that using dev containers could be possible with the JetBrains Gateway program, but it's hard to tell if this only works with certain JetBrains IDEs.