update(README.md): update contributing section

[alacuku]

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design
/kind documentation

/kind failing-test

/kind feature

If this PR will release a new chart version please make sure to also uncomment the following line:

/kind chart-release

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area falco-chart

/area falco-exporter-chart

/area falcosidekick-chart

/area event-generator-chart

/area k8s-metacollector

What this PR does / why we need it:

Update the contributing section.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Checklist

• Chart Version bumped
• Variables are documented in the README.md
• CHANGELOG.md updated

[poiana]

LGTM label has been added.

Git tree hash: 5ea356ce8ad3a32bb8263e82ea5484bc6908cfe2

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alacuku, Issif

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