docs(metrics): Add docs for metrics in Sentry-CLI

[elramen]

DESCRIBE YOUR PR

Metrics is being added to sentry-cli. This PR adds documentation about how to use metrics in the cli.

IS YOUR CHANGE URGENT?

Help us prioritize incoming PRs by letting us know when the change needs to go live.

• [x] None: Not urgent. Will not merge PR until new sentry-cli release is made.

PRE-MERGE CHECKLIST

Make sure you've checked the following before merging your changes:

• [x] Checked Vercel preview for correctness, including links
• [x] PR was reviewed and approved by any necessary SMEs
• [x] PR was reviewed and approved by a member of the Sentry docs team

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Name	Status	Preview	Comments	Updated (UTC)
sentry-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 28, 2024 2:44pm

[codecov[bot]]

Bundle Report

Changes will increase total bundle size by 93 bytes :arrow_up:

Bundle name	Size	Change
sentry-docs-server	7.42MB	102 bytes :arrow_up:
sentry-docs-edge-server	461.47kB	3 bytes :arrow_down:
sentry-docs-client	6.18MB	6 bytes :arrow_down: