v0.3.0

What's Changed

• docs: add example to README by @alecthomas in 8b5b95e
• docs: brief feature list in README by @alecthomas in 2f62ffe
• fix: parser errors are formatted as <file>:<line> by @alecthomas in 7004f40
• feat: improve validation around option usage with one-shot by @alecthomas in bd362ba