docs: add warning only rust-based sgxkit is officially supported

[ozwaldorf]

Why?

Adds notice and link to sgx edge doc about sgxkit

Contribution checklist?

• The commit messages are detailed
• The build command runs locally
• Assets or static content are linked and stored in the project
• Document filename is named after the slug
• You've reviewed spelling using a grammar checker
• For documentation, guides or references, you've tested the commands and steps
• You've done enough research before writing

Security checklist?

• Sensitive data has been identified and is being protected properly
• Injection has been prevented (parameterized queries, no eval or system calls)
• The Components are escaping output (to prevent XSS)

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[changeset-bot]

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Latest commit: b63c1bd

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