Overwrite default setup.md

[CallumWalley]

Hey all,

There are quite a few knacks to getting onto our platform, which has led to me completely replacing 'setup.md' with a site specific version.
Being able to nominate a replacement 'setup.md' in the yaml file would be useful.
Thoughts?

[tkphd]

Interesting -- should be straight-forward. I would probably:

• move the contents of setup.md into _includes/snippets_library/setup.snip, then
• put {% include {{ site.setup %}} as the content of setup.md, and
• write setup = "/snippets_library/setup.snip" into the top-level _config.yml.
• To customize, move your setup.md into _includes/snippets_library/institution_cluster/setup.snip and
• set the corresponding path in _includes/snippets_library/institution_cluster/_config_options.yml.
• Build the site with make --always-make site HPC_JEKYLL_CONFIG=_includes/snippets_library/institution_cluster/_config_options.yml.

Should work, I think?