v0.2

New features:

• Allow running in polling mode (@talex5 #44).

Other changes:

• Update to liburing 2.1 (@talex5 #46).
• Remove bigstringaf dependency (@talex5 #43).
• Cmdliner is only needed for tests (@talex5 #45).
• Remove test dependencies on Bos and Rresult (@talex5 #40).
• Address Fmt.strf deprecation error (@bikallem #38).
• Update to cstruct 6.0.1 for shiftv (@talex5 #36).