Adding Asciidoc map preview script and left TOC JS file

[bscott-rh]

This PR adds a bash script for building and publishing JTBD maps to GitHub Pages, as well as a javascript file that adds collapsible elements to the left hand nav.

Prerequisites:

• writer has enabled GitHub Pages in their fork of the openshift-docs repo
• writer has a gh-pages branch in their fork (should be created automatically by the prior step)
• writer has configured their fork's Pages settings to build from the gh-pages branch (this is the default setting)
• writer has some JTBD maps in the maps/ directory, with corresponding assemblies and modules in the assemblies/ and modules/ directories respectively

The script is meant to be run from the root of the openshift-docs repo in a feature branch. The script checks out the gh-pages branch in a separate worktree in /tmp, uses asciidoctor to build the maps/navigation.adoc file, and pushes the resulting HTML into the gh-pages branch, which triggers GitHub Pages to host the HTML.

The script produces two URLs, one being the preview URL for the changes that were just pushed, in the following format:
https://${GH_USERNAME}.github.io/${GH_REPO}/${BRANCH}/navigation.html
and one being the URL to check the status of the Pages deployment in GitHub (to check for errors, or just see when the preview is ready):
https://github.com/${GH_USERNAME}/${GH_REPO}/deployments

[ocpdocs-previewbot]

🤖 Tue Jul 07 17:55:21 - Prow CI generated the docs preview:

https://114783--ocpdocs-pr.netlify.app/

[openshift-ci]

@bscott-rh: all tests passed!

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