docs: add secret_ref.md into sidebar

[seeflood]

Signed-off-by: seeflood zhou.qunli@foxmail.com

What this PR does:
add secret_ref.md into sidebar

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov]

Codecov Report

Merging #711 (1d9b286) into main (e975d73) will not change coverage.
The diff coverage is n/a.

❗ Current head 1d9b286 differs from pull request most recent head 333295e. Consider uploading reports for the commit 333295e to get more accurate results

@@           Coverage Diff           @@
##             main     #711   +/-   ##
=======================================
  Coverage   60.89%   60.89%           
=======================================
  Files         122      122           
  Lines        6432     6432           
=======================================
  Hits         3917     3917           
  Misses       2133     2133           
  Partials      382      382           

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