`GroupConfig`: Added some documentation explaining fields & defaults.

Fortune for rematch's current commit: Half curse − 半凶

src/main.rs

@@ -65,10 +65,21 @@ fn initialise() -> eyre::Result<()>
     Ok(())
 }
 
+/// Provides the group output writer with references to the byte-strings to be used to delimit single groups' output & to delimit each input string (or line)'s output.
+///
+/// The defaults are `\n` (LF-literal) for [line_delimiter], and `\t` for [field_delimiter], see the fields for more information.
 #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord/*, Copy*/)]
 pub struct GroupConfig<'a>
 {
+    /// Delimits the output of each individual input string.
+    ///
+    /// By default, this is a newline `\n` character.
     pub line_delimiter: &'a [u8],
+    /// Delimits the output of each requested capture group (per [line_delimiter].)
+    /// If there is only 1 (or less) requested groups (that may be *empty/unmatched*, are **not** *invalid*,)
+    /// then there is no field delimit for that individual output string line.
+    ///
+    /// By default, this is a tab literal `\t` character.
     pub field_delimiter: &'a [u8],
 }