achieve BNF

[tu6ge]

valitron/src/register/mod.rs

Lines 45 to 60 in c6adefc

	/// # Register rules
	///
	/// **Feild support multiple formats:**
	/// - `field1` used to matching struct field
	/// - `0`,`1`.. used to matching tuple item or tuple struct field
	/// - `[0]`,`[1]` used to matching array item
	/// - `[foo]` used to matching struct variant, e.g. `enum Foo{ Color { r: u8, g: u8, b: u8 } }`
	///
	/// The above can also be combined:
	/// - `field1.0`
	/// - `0.color`
	/// - `[12].1`
	/// - `foo.1[color]`
	/// - more combine
	///
	/// TODO add BNF