Fix typos in c-cpp-book markdown files

[PierreBhs]

While reading the c-cpp-book, I've noticed some typos:

• ch05: 'would be cause' → 'would cause'
• ch07: 'belw' → 'below'
• ch08: 'have been to' → 'have been added to'
• ch09: 'situation that result' → 'situations that result'
• ch09: add missing '-' before 'if let'

Hope this helps!

Edit: I have also noticed that in ch09-error-handling, the "Rust error handling sections" appears multiple times, with one being an exact duplicate. The "Rust Option type" also appears twice. I can update it but this would require bigger changes. Should I do it in this PR or in another one?

[PierreBhs]

@microsoft-github-policy-service agree