Add make command to docs to install dependencies

[ren510dev]

What this PR does / why we need it:

Add dependency install command for web config to documentation.
Developers run this command before building the Control-Plane.

Which issue(s) this PR fixes:

Fixes #4546

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[kentakozuka]

Thanks for the PR!
Could you update your commit messages and add Sign-off-by information? We're following the DCO for now, and requires signing off every commits 🙏
https://pipecd.dev/docs/contribution-guidelines/contributing/#contributor-license-agreement

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.92%. Comparing base (6e9660d) to head (69109f4).
Report is 821 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4572      +/-   ##
==========================================
+ Coverage   29.91%   29.92%   +0.01%     
==========================================
  Files         220      220              
  Lines       25892    25892              
==========================================
+ Hits         7745     7749       +4     
+ Misses      17499    17496       -3     
+ Partials      648      647       -1     

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[khanhtc1202]

Nice catch, thanks 🙌

[khanhtc1202]

@GotoRen Please sign-off your commit to make the CI passed 🙏
https://pipecd.dev/docs/contribution-guidelines/contributing/#contributor-license-agreement

[ren510dev]

I signed-off !!

[kentakozuka]

Thanks 🚀