MAINT: Let CircleCI render PRs to improve PR review

[sappelhoff]

closes #81

• added a circle ci config to install jekyll and build the website
• I added Eric's app that directly links to the main artifact (index.html in our case) from the GitHub PR: https://github.com/larsoner/circleci-artifacts-redirector-action ... see also [INFRA] Link to doc builds in CI checks bids-specification#315

Issues

• the website is not rendered correctly. Due to missing dependencies in the Gemfile?
• the direct link to artifacts (GitHub action) may only work upon merging this, see Note in this README
• speed up the build by caching everything that needs to be installed (done in sappelhoff@adef5ff)

current artifacts: https://circleci.com/gh/bids-standard/bids-website/6#artifacts/containers/0

see for example the index.html: https://6-38337026-gh.circle-artifacts.com/0/home/circleci/project/_site/index.html

[robertoostenveld]

@poldrack this relates to what we were shortly discussion yesterday regarding building the website for pull requests. Just that you are aware that @sappelhoff already initiated action on this.

[effigies]

I think the main issue is with finding the CSS:

bids-website/_layouts/default.html

Line 68 in fa20bfe

<link rel="stylesheet" href="{{ '/assets/css/style.css' | relative_url }}">

I think we need to drop the initial /. It may cause some issues if we have HTML files in deeper directories, but we can worry about that later.

Edit: Actually, this is probably an issue for all cases where "/assets appears in the template.

[effigies]

This doesn't seem to be working. Do we just want to add:

.circleci/artifact_path:

0/html/index.html

[sappelhoff]

@effigies this seems to work now. Thanks to your changes (with minor correction)