Update GLFM docs with new headers
- Add headers and anchors for individual input and output files.
- These are convenient to provide direct links to documentation for individual files, from source code and MRs.
- Add links directly to actual files in gitlab repo
- Add missing GFM spec file and remove from gitignore for link target
- Add placeholders for other GLFM input and example snapshot files for link targets
Edited by Chad Woolley