v0.4

New features:

• Add Uring.timeout (@bikallem #59).
• Add Uring.read and Uring.write (@haesbaert #62). These are simple wrappers for read(2) and write(2).
• Add Uring.unlink (@talex5 #65). This uses unlinkat(2), and so can also be used to remove directories.
• Add support for uring probes (@talex5 #70). Allows checking whether a feature is supported by the kernel at runtime.
• Rename peek to get_cqe_nonblocking (@talex5 #67). The old name was confusing because it does remove the item from the ring.
• Update to liburing 2.2 (@talex5 #56).
• Add Uring.active_ops (@talex5 #68). Avoids needing to track the value returned by submit, which is important as it is sometimes called automatically.
• Add Uring.iov_max constant (@talex5 #76).
• Add Uring.get_debug_stats (@talex5 #64). This should make it easier to check that the uring is behaving as expected.

Performance:

• Introduce a Sketch buffer per Uring (@haesbaert #63). The main motivation of this change is to avoid having one malloc per packet in readv(2), writev(2) and friends.
• Use submit_and_wait where appropriate (@haesbaert #69).
• Add a readv benchmark (@talex5 #64).
• Avoid unnecessary use of CAMLparam in the C stubs (@haesbaert #61).

Bug fixes:

• Prevent ring from being used after exit (@talex5 #78).

Build changes:

• Remove use of notty for formatting benchmark results (@talex5 #71). It prevented uring from being tested on OCaml 5.
• Use MDX for README (@talex5 #57).
• Convert tests to MDX (@talex5 #58 #73).
• Use opam-repository syntax for license (@kit-ty-kate #72).
• Remove internal is_dirty flag (@talex5 #77).