Update deepforge-extension.json to include python dependencies

[umesh-timalsina]

We should include python dependencies (along with preferred installer (conda, pip), any channels to be added etc..) in the deepforge-extension.json.

[brollb]

If we are centering around conda in deepforge (deepforge-dev/deepforge#1402), it might make more sense to use conda environment files rather than specifying all these things in our own way (reinventing the wheel).

[brollb]

This is blocked by the method of specifying dependencies in deepforge: deepforge-dev/deepforge#1466