docs: add page for long tasks causing frame drops

[armcknight]

Pre-merge checklist

If you work at Sentry, you're able to merge your own PR without review, but please don't unless there's a good reason.

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

Description of changes

Add a new page for Frame Drop profiling issues.

TODO

• new profile screenshot after we can fix the problem with the blamed frame being chopped up
• once docs: mobile app profiling metrics #7660 is merged, link to "energy usage" section on that page from here

Extra resources

• Sentry Docs contributor guide

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Name	Status	Preview	Comments	Updated (UTC)
sentry-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 19, 2023 0:22am

[lizokm]

I know this is a work in progress, but have made some language suggestions. Let me know when it's ready and I can look at it again :)

[indragiek]

We should replace the screenshot before publishing this

[armcknight]

We should replace the screenshot before publishing this

Yup, I already have this as a TODO item in the description!

[lizokm]

This is looking really good!