:book: Update documentation before Kubecon

[michaelryanpeter]

Update the documentation to reflect the current development state of OLM 1.0.

Content:

• [ ] Remove "Why OLM v1?" in favor of the "OLM v1 Overview" introduced in #692
• [ ] Quickstart/installation
• [x] Adding a catalog of extensions https://github.com/operator-framework/operator-controller/pull/694
• [x] Querying a catalog https://github.com/operator-framework/operator-controller/pull/696
• [x] Installing an extension https://github.com/operator-framework/operator-controller/pull/700
• [ ] Version ranges/Semver support (just adding links to draft docs for now).
• [x] Deleting an extension https://github.com/operator-framework/operator-controller/pull/700

/assign