Improve compatibility documentation

[PProfizi]

Description of the feature

Too many issues regard compatibility issues, especially with Ansys 2021 R1.
It seems the documentation is not clear.
The installation command is actually wrong when using Ansys 2021 R1.

Steps for implementing the feature

• The compatibility table should be at the start of the "Getting Started" page
• It mentions having to synchronize the ansys.grpc.dpf module but not explicitly the server and python client compatibility
• The "Architecture" section mentions Ansys 2021R2 as required while the "Installation with PIP" section mentions "Ansys 2021 R1 or later" and gives only the command pip install ansys-dpf-core which is wrong is using Ansys 2021R1 (should be pip install ansys-dpf-core<0.3.0)
• The Ansys 2021R1 row of the table should be visually separated in some way (thicker boundaries?)
• We might actually want to mention compatibility in the ReadMe, along with specifying that the installation command is for Ansys 2021 R2 onward.
• We can also customize the Issue template to add a tick box with "I made sure I am following the Compatibility guidelines", with an hyperlink to the doc.

Useful links and references

No response

[PProfizi]

@rlagha @cbellot000 @anslpa FYI