Docs for inheritance

[artberger]

Adding to the concepts page and linking to existing docs on transformation and auth config as examples

Context

Based on discussion in Slack.

Checklist:

• I included a concise, user-facing changelog (for details, see https://github.com/solo-io/go-utils/tree/main/changelogutils) which references the issue that is resolved.
• N/A If I updated APIs (our protos) or helm values, I ran make -B install-go-tools generated-code to ensure there will be no code diff
• I followed guidelines laid out in the Gloo Edge contribution guide
• I opened a draft PR or added the work in progress label if my PR is not ready for review
• N/A I have performed a self-review of my own code
• N/A I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• N/A I have added tests that prove my fix is effective or that my feature works

[github-actions]

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