feat: Add help_heading to command

- allows setting a custom help heading for the command
- implements getter for help heading

Author: gortavoher

clap_builder/src/builder/command.rs

@@ -104,6 +104,7 @@ pub struct Command {
     current_disp_ord: Option<usize>,
     subcommand_value_name: Option<Str>,
     subcommand_heading: Option<Str>,
+    help_heading: Option<Option<Str>>,
     external_value_parser: Option<super::ValueParser>,
     long_help_exists: bool,
     deferred: Option<fn(Command) -> Command>,
@@ -3701,6 +3702,24 @@ impl Command {
         self.subcommand_heading = heading.into_resettable().into_option();
         self
     }
+
+
+    /// Set a custom help_heading for the command
+    #[inline]
+    #[must_use]
+    pub fn help_heading(mut self, heading: impl IntoResettable<Str>) -> Self {
+        self.help_heading = Some(heading.into_resettable().into_option());
+        self
+    }
+
+    /// Get the help heading specified for this argument, if any
+    #[inline]
+    pub fn get_help_heading(&self) -> Option<&str> {
+        self.help_heading
+            .as_ref()
+            .map(|s| s.as_deref())
+            .unwrap_or_default()
+    }
 }
 
 /// # Reflection
@@ -4229,7 +4248,7 @@ impl Command {
     pub fn is_hide_set(&self) -> bool {
         self.is_set(AppSettings::Hidden)
     }
-
+    
     /// Report whether [`Command::subcommand_required`] is set
     pub fn is_subcommand_required_set(&self) -> bool {
         self.is_set(AppSettings::SubcommandRequired)
@@ -5218,6 +5237,7 @@ impl Default for Command {
             current_disp_ord: Some(0),
             subcommand_value_name: Default::default(),
             subcommand_heading: Default::default(),
+            help_heading: Default::default(),
             external_value_parser: Default::default(),
             long_help_exists: false,
             deferred: None,