write docs

[todo]

vers/vers-core/src/lib.rs

Lines 18 to 23 in 2c78736

	/// TODO: write docs
	pub mod errors;
	/// TODO: write docs
	pub mod filters;
	/// TODO: write docs
	pub mod machine;

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This issue was generated by todo based on a TODO comment in 2c78736. It's been assigned to @reynn because they committed the code.