Added table of dependencies versions to README

[paskino]

Description

• closes Add tested matrix to readme #2091

After discussion with @hrobarts we decided to not remove the original conda install commands as the new proposed one didn't seem simple.

Also the old text made clear what the role of the additional dependencies is and even how to get ASTRA for CPU or GPU.

We added the new command pointing to the environment file with the instruction that it was installing the software necessary for CIL-Demos with tested versions.

Checklist

• I have performed a self-review of my code
• I have added docstrings in line with the guidance in the developer guide
• I have updated the relevant documentation
• I have implemented unit tests that cover any new or modified functionality
• CHANGELOG.md has been updated with any functionality change
• Request review from all relevant developers
• Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License
• I confirm that the contribution does not violate any intellectual property rights of third parties

[gfardell]

Do we want to also update the conda instructions to use the env files here:
TomographicImaging/scripts#3

Hannah has drafted something here:
https://github.com/TomographicImaging/Build-scripts/blob/2709ecd3ba2c3b30418ad71d38094c3e16450d28/README.md#installation-with-conda

[gfardell]

It seems very clear to me! I think it's a good change. The tested versions we can update as we iterate.

[casperdcl]

well that was easy