Add What this PR does / why we need it section

[bmnidhin]

What this PR does / why we need it:

• Pull template don't have a What this PR does / why we need it: section so contributes needed to add that heading manually. This PR adds that to the template. Used the same wording used here https://github.com/kubernetes/kubernetes/blob/a2106b5f73fe9352f7bc0520788855d57fc301e1/.github/PULL_REQUEST_TEMPLATE.md?plain=1#L28C6-L28C41

• It is added as a h2 level heading

[k8s-ci-robot]

Hi @bmnidhin. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[Priyankasaggu11929]

Thanks for the PR @bmnidhin!

Requested few minor changes.

/ok-to-test

[Priyankasaggu11929]

Thank you @bmnidhin. Please squash the commits to one.

/lgtm
/approve

/hold
for commit squash

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bmnidhin, Priyankasaggu11929

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