Support for using VSCode integrations in particular python and clangd

It should be even easier to easyjet with VSCode. See the new README section for how to get feedback like this:

Besides tooltips and tab-completion, header includes can also function as hyperlinks.

In python you can preview (peek) definitions of code even in athena packages from within your source file

Also you can get syntax suggestions for return type hints (grey -> None for no return here)

Note: we may wish to cross-check the list of flake8 checks/ignores, as this list is taken from athena as is the rest of the .vscode setup.