Add How To Build Instructions

[JBoggsy]

Presently, the Soar website has a page with instructions to build Soar with ROS1 based on Lizzie's code (https://soar.eecs.umich.edu/development/BuildingSoarRos/), but no page describing how to build Soar by itself. This would be nice for those of us modifying Soar directly for research, etc.

[moschmdt]

I assume you refer to the development/ prerequisite steps in the main README file of the Soar repo?
Maybe a link to that file should be sufficient with a short description, so nothing is repeated? In my opinion, this would remain maintainable without repeating content.

[garfieldnate]

@natederbinsky also suggested that we point to the GH Action definitions instead, maybe with an explanation of what section to look at. The Action definitions should always contain the most up-to-date info on building Soar.