📚 Docs: Fix import and comma issues

[ghost]

Description

• Fixed an import issue in monitor.md (that was added with 📚 Docs: Fix typos, and make middleware documentation more consistent #2408, Sorry about that!)
• Added cache package to the custom key and expire time example
• Added proxy package to the DoDeadline example
• Added log.Fatal to skip and timeouŧ examples

Type of change

• This change requires a documentation update

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation - /docs/ directory for https://docs.gofiber.io/

Commit formatting:

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[gaby]

Lgtm

[li-jin-gou]

LGTM