Add audit doc

[soltysh]

This is copy of #1168 which already have tech approval (so I'm applying the label based on that) , I'm recreating it so it's part of 1.4.

@devin-donnelly ptal

@janetkuo @sttts fyi

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This change is

[devin-donnelly]

Review status: 0 of 2 files reviewed at latest revision, 3 unresolved discussions.

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docs/admin/audit.md, line 12 [r1] (raw file):

## Audit in Kubernetes

If this is where we're introducing the context of Audit in Kubernetes, it would be a good place to give a one- or two-sentence description of what Audit does and why it exists.

Something like "Kubernetes Auditing makes sure that..." or "Kubernetes Audit provides..."

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docs/admin/audit.md, line 50 [r1] (raw file):

- `audit-log-maxsize` - specifies maximum size in megabytes of the audit log file before it gets rotated. Defaults to 100MB

Audit logs are being appended if the file already existed or a new one will be

"If an audit log file already exists, Kubernetes appends new audit logs to that file. Otherwise, Kubernetes creates an audit log file at the location you specified in audit-log-path. If the audit log file exceeds the size you specify in audit-log-maxsize, Kubernetes will rename the current log file by appending the current timestamp on the file name (before the file extension) and create a new audit log file.

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docs/admin/audit.md, line 54 [r1] (raw file):

renamed by putting the current timestamp at the end name of the file name (before
the file's extension)
Whenever a new logfile get created, old log files may be deleted. This policy is

Kubernetes may delete old log files when creating a new log file; you can configure how many files are retained and how old they can be by specifying the audit-log-maxbackup and audit-log-maxage options.

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Comments from Reviewable

[soltysh]

Comments addressed, ptal.

[devin-donnelly]

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Review status: 0 of 2 files reviewed at latest revision, 3 unresolved discussions.

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Comments from Reviewable

[devin-donnelly]

Looks good, but there are some merge conflicts. I can't merge until they're resolved. @soltysh , would you mind taking a look?

[soltysh]

@devin-donnelly rebased

[devin-donnelly]

Thanks. Merging.