Document custom error types

src/lenient_parse.gleam

@@ -65,11 +65,32 @@ pub fn to_int(text: String) -> Result(Int, ParseError) {
 }
 
 pub type ParseError {
+  /// Represents an error when an invalid character is encountered during
+  /// parsing. The `String` parameter contains the invalid character.
   InvalidCharacter(String)
+
+  /// Represents an error when the input string is empty or contains only
+  /// whitespace.
   WhitespaceOnlyOrEmptyString
+
+  /// Represents an error when an underscore is in an invalid position within
+  /// the number string.
   InvalidUnderscorePosition
+
+  /// Represents an error when a decimal point is in an invalid position within
+  /// the number string.
   InvalidDecimalPosition
+
+  /// Represents an error that occurs when Gleam's built-in `float.parse` fails
+  /// after our custom lenient parsing steps. This indicates that even with our
+  /// more permissive parsing rules, the string still couldn't be converted to a
+  /// float.
   GleamFloatParseError
+
+  /// Represents an error that occurs when Gleam's built-in `int.parse` fails
+  /// after our custom lenient parsing steps. This indicates that even with our
+  /// more permissive parsing rules, the string still couldn't be converted to
+  /// an integer.
   GleamIntParseError
 }