docs: add footer to docs

[hanxiao]

[github-actions]

Thanks for your contribution ❤️
💔 Unfortunately, this PR has one ore more bad commit messages, it can not be merged. To fix this problem, please refer to:

• Commit Message Guideline for the First Time Contributor
• Contributing Guideline

Note, other CI tests will not start until the commit messages get fixed.

This message will be deleted automatically when the commit messages get fixed.

[github-actions]

Latency summary

Current PR yields:

• 🐢🐢 index QPS at 1709, delta to last 3 avg.: -9%
• 😶 query QPS at 33, delta to last 3 avg.: -3%

Breakdown

Version	Index QPS	Query QPS
current	1709	33
0.8.11	1840	35
0.8.10	1910	35
0.8.9	1944	32

Backed by latency-tracking. Further commits will update this comment.