release: v0.3.0

CHANGELOG:
- refactor: add "thread-safe" versions of certain functions
- perf(close): add translation step to simplify minfd/keep_fds
  specification
- perf(fditer): override FdIter::min() and Fditer::max() for efficiency
- ci: build for more supported targets
- feat(fditer): expose "possible" status of an FdIter
- fix: fix internal bugs
- refactor: major internal refactoring
- doc: improved documentation (and warnings)
- test: improved tests

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "close_fds"
-version = "0.2.2"
+version = "0.3.0"
 edition = "2018"
 
 description = "A library that makes it easy to close all open file descriptors."