Add the ability to read Environment Variables from other locations

[nils-a]

I'm currently in a project where people are using different tooling.

They are using environments that are very similar to this environment settings, but reside in a this-tool.env.json file. It would be nice if we could easily load that file and "re-use" the settings. (Currently I'm copy-pasting their environments content into .vscode/settings.json.)

[asos-gurpreetsingh]

not only the environment variable, say I want to store some long static text in a file and use that in a variable later , how do i do that. It would be easier to keep things like json content in json files (easy to format) and load it in a variable where needed

[franck-chester]

I've just discovered the vscode secrets extension, but noticed the environment variables it injects via EnvironmentVariableCollection do not seem to be picked up by the REST Client extension?

I can use processEnv PATH or processEnv %workspaceVariable with all other environment variables, works great, but it doesn't pick the one managed via the vs-code secret extension