Feature: Establish glossary and setup Kubewarden terms variable expansion

[viccuad]

From https://github.com/kubewarden/docs/pull/393#discussion_r1562516046.

Acceptance criteria

• [x] Establish a glossary as a part of the main documentation set. Also done in #396.
• [x] #396 Update docs to substitute terms exclusive to Kubewarden (such as PolicyServer, policy-server, kwctl). They should link to their reference pages. For example, the CRD docs, a reference glossary page, etc. Example: [[< policy-server-component >]]
• Follow https://kubernetes.io/docs/contribute/style/style-guide for those terms that are Kubernetes resources.

[flavio]

I think we should tackle this issue by doing a small PR that introduces the terms and update the docusaurus infrastructure to use them.

Then we can go on and replace all the terms

@jhkrug can you point us to some docusarus doc/examples? I tried to find them sometimes ago, but I failed

[jhkrug]

396 I think is what we are looking for.

There is some Docusaurus docs at https://docusaurus.io/docs/api/docusaurus-config#preprocessor