docs: modify git commit command line and add signature reference documentation

Created by: zhaohuiweixiao

Signed-off-by: zhaohuihui zhaohuihui_yewu@cmss.chinamobile.com

What type of PR is this?

/kind documentation

What this PR does / why we need it:

kubesphere console community requires signature(GPG or S/MIME) verification when submitting code, but it is not mentioned in the development-workflow.md document about how to submit a PR, also it is not reflected in the git commit submission command. The error git commit command mislead the commiters when submit a commit, Thus this result in repeated submissions or modify commit message.

Special notes for reviewers:

/assign harrisonliu5

Does this PR introduced a user-facing change?

None