Add contributing and readme to docs approvers approvable scope

[khanhtc1202]

What this PR does:

Why we need it:

Which issue(s) this PR fixes:

Fixes #

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):

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 28.87%. Comparing base (649e8f6) to head (eb2b6db).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6538   +/-   ##
=======================================
  Coverage   28.87%   28.87%           
=======================================
  Files         560      560           
  Lines       59955    59955           
=======================================
  Hits        17313    17313           
  Misses      41321    41321           
  Partials     1321     1321           

Flag	Coverage Δ
.	23.29% <ø> (ø)
.-pkg-app-pipedv1-plugin-analysis	32.64% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	58.67% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	67.63% <ø> (ø)
.-pkg-app-pipedv1-plugin-scriptrun	54.83% <ø> (ø)
.-pkg-app-pipedv1-plugin-terraform	38.65% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	33.92% <ø> (ø)
.-pkg-app-pipedv1-plugin-waitapproval	52.71% <ø> (ø)
.-pkg-plugin-sdk	50.34% <ø> (ø)
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	25.51% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

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[eeshaanSA]

Lgtm thanks!