site: Add netlify.toml

[ahmetb]

From: https://github.com/kubernetes/community/blob/master/github-management/subproject-site-requests.md#example-netlify-configuration

[corneliusweig]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahmetb, corneliusweig

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[codecov-io]

Codecov Report

Merging #520 into master will decrease coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #520      +/-   ##
==========================================
- Coverage   59.12%   58.85%   -0.28%     
==========================================
  Files          23       23              
  Lines        1003     1011       +8     
==========================================
+ Hits          593      595       +2     
- Misses        350      358       +8     
+ Partials       60       58       -2

Impacted Files	Coverage Δ
internal/index/indexscanner/scanner.go	66.1% <0%> (-6.45%)	⬇️

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