Add rust SDK functionality table

[domgreen]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:

/kind breaking
/kind bug
/kind cleanup
/kind documentation
/kind feature
/kind hotfix

What this PR does / Why we need it:

Adding tables for Rust SDK

Special notes for your reviewer:

[domgreen]

I think we can also add a table of all SDKs somewhere once ive made a first pass of the remaining ones 👍 which can be a one stop shop.

[agones-bot]

Build Succeeded 👏

Build Id: 94428d1b-d763-498d-8bb1-bc73af38819e

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:1.15.0-430e660
• image: gcr.io/agones-images/agones-ping:1.15.0-430e660
• Linux C++ SDK (build): agonessdk-1.15.0-430e660-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.15.0-430e660.zip

A preview of the website (the last 30 builds are retained):

• https://430e660-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2082/head:pr_2082 && git checkout pr_2082
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.15.0-430e660

[roberthbailey]

The table lgtm. @markmandel - can you confirm that the Rust SDK does implement all of these functions?

[markmandel]

Confirmed!

[google-oss-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: domgreen, markmandel

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• OWNERS [markmandel]

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[google-oss-robot]

New changes are detected. LGTM label has been removed.

[agones-bot]

Build Succeeded 👏

Build Id: 8ab5a97a-854b-47f6-810d-5028f45e758b

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:1.15.0-f61ea57
• image: gcr.io/agones-images/agones-ping:1.15.0-f61ea57
• Linux C++ SDK (build): agonessdk-1.15.0-f61ea57-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.15.0-f61ea57.zip

A preview of the website (the last 30 builds are retained):

• https://f61ea57-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/googleforgames/agones.git pull/2082/head:pr_2082 && git checkout pr_2082
• helm install ./install/helm/agones --namespace agones-system --name agones --set agones.image.tag=1.15.0-f61ea57