Migrate to mkdocs

[ayberk]

What type of PR is this?
/kind documentation

What this PR does / why we need it:

• Migrates the docs from gitbook to mkdocs because gitbook is deprecated. Here's what the new docs looks like: https://ayberk.github.io/cloud-provider-aws/
• Adds a new github action to deploy docs automatically when they're updated

PS: mkdocs doesn't builds the site into the root folder, so we'll have to change the folder for Github Pages to / (from repo settings).

I'll delete the gitbook related stuff on a different PR. If I delete the netlify.toml, checks fail.

NONE

[k8s-ci-robot]

Hi @ayberk. 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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[ayberk]

/hold

[ayberk]

/unhold

[nckturner]

/ok-to-test

[nckturner]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ayberk, nckturner

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