Narwhals v0.9.11

Changes

✨ Enhancements

• enh: series and expr round method (#306)
• enh: slice, starts_with, tail methods for str namespace (#305)

🛠️ Other improvements

• ci: issue template correction (#303)

Thank you to all our contributors for making this release possible!
@DeaMariaLeon, @FBruzzesi and @MarcoGorelli