e3-704: add documentation for using e3-build, and add markdown linting
Documentation files have been created for:
- using a formula to update GitLab wrappers and generate a new specification file
- using a specification file to build a new e3 environment
Both files are linked to from the main README file.
This MR also includes linting of the Markdown files. This probably should have been a separate MR.
Edited by Wayne Lewis