README / ADDITIONAL.md: small link and alt-text corrections #5212

Problem

Three small corrections to existing entries, each still present on v2/main:

1. In ADDITIONAL.md, the icon for the llm-analysis-assistant entry has the alt text of a different project (copied from another entry). Verified.
2. In ADDITIONAL.md, the OpenTools entry links a GitHub organization that is reported to be gone. Unverified.
3. The Community link in README.md and the AgentR link in ADDITIONAL.md are reported to be dead. Unverified.

Expected

Fix item 1; check each URL in items 2 and 3 before changing it.

Prior work

• fix(docs): correct copy-pasted alt text on llm-analysis-assistant favicon #4169 by @killertcell428
• docs: remove dead opentoolsteam attribution link from ADDITIONAL.md #4675 by @wisdom222
• Fix dead Discussions link in README and AgentR link in ADDITIONAL.md #4884 by @pratikgx

The PR(s) above targeted the pre-refactor code and are closed as part of the backlog triage in #4875; this issue is where the work continues, with the PR(s) as a prototype. Thank you to their authors.