Doc the development dependencies

[v0y4g3r]

Since #2007 is merged, we now need clang-format installed to run cargo commands otherwise it will complain:

error: failed to run custom build command for `opendal-c v0.1.0 (/incubator-opendal/bindings/c)`

Caused by:
  process didn't exit successfully: `/incubator-opendal/target/debug/build/opendal-c-20286dcc7e0a1a6f/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'clang-format must succeed: Os { code: 2, kind: NotFound, message: "No such file or directory" }', bindings/c/build.rs:35:10
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

We may add a Development dependencies to guide developers to install clang-format first or tell users about missing clang-format dependency when build script panics:

https://github.com/apache/incubator-opendal/blob/640a7d23b67f6b7988112b6fb75d4d53b6790840/bindings/c/build.rs#L35