Add some missing doc comments

Signed-off-by: Ben Aaron Goldberg <ben@benaaron.dev>

src/lib.rs

@@ -83,6 +83,7 @@ impl InstanceSettings {
 		Self::parse_prefstring(pref_string)?.select_pronoun(&self, name)
     }
 
+	/// Parse a pref_string.
 	pub fn parse_prefstring(pref_string: Option<&str>) -> Result<UserPreferences, ParseError> {
 		match pref_string {
 			Some(pref_string) => UserPreferences::from_prefstring(pref_string),

src/user_preferences/mod.rs

@@ -83,6 +83,16 @@ pub trait Preference {
 		BASE32_NOPAD.encode(&self.into_prefstring_bytes())
 	}
 
+	/// Select a pronoun for today using this Preference's WeightedTable.
+	///
+	/// Is shorthand for
+	///
+	/// ```
+	/// # use pronouns_today::InstanceSettings;
+	/// # let settings = InstanceSettings::default();
+	/// # let seed = &[];
+	/// self.into_weighted_table(settings)?.select_today(seed)
+	/// ```
 	fn select_pronoun<'a>(&self, settings: &'a InstanceSettings, name: Option<&str>) -> Result<&'a Pronoun, ParseError> {
 		let seed = match name {
 			Some(name) => name.as_bytes(),