Expand glossary and use {{< gloss >}} to use as metadata for See Also and SEO

[geeknoid]

We should expand the glossary, and make use of the site's {{< gloss >}} feature that allows pop ups for glossary terms. Some terms to include:

• [x] Mesh Configuration Protocol (MCP)
• [x] Secret Discovery Protocol (SDS)
• [ ] Ingress Gateway
• [ ] Egress Gateway
• [x] Sidecar
• [x] SPIFEE
• [ ] Container Network Interface (CNI)
• [x] Virtual Service
• [ ] Destination Rule
• [ ] Custom Resource Definition
• [ ] Circuit breaker
• [ ] Load shedding
• [ ] Strong Identity

I'll add more as I think of 'em.