Typo fix in drag-and-drop documentation (#7750)

* [x] I have followed the instructions in the PR template

Adding periods to the end of sentences and fixes a grammar mistake on
documentation for the drag-and-drop code to become consistent with the
rest of the documentation.

The documentation for `Ui::dnd_drop_zone` could've used the word "its"
instead of "the" to replace "it", but I think "the" more clearly refers
to the `Frame` since "its" has been used to refer to the drop-zone
already.

crates/egui/src/context.rs

@@ -4016,7 +4016,7 @@ impl Context {
     /// Is this specific widget being dragged?
     ///
     /// A widget that sense both clicks and drags is only marked as "dragged"
-    /// when the mouse has moved a bit
+    /// when the mouse has moved a bit.
     ///
     /// See also: [`crate::Response::dragged`].
     pub fn is_being_dragged(&self, id: Id) -> bool {
@@ -4030,7 +4030,7 @@ impl Context {
         self.interaction_snapshot(|i| i.drag_started)
     }
 
-    /// This widget was being dragged, but was released this pass
+    /// This widget was being dragged, but was released this pass.
     pub fn drag_stopped_id(&self) -> Option<Id> {
         self.interaction_snapshot(|i| i.drag_stopped)
     }

crates/egui/src/response.rs

@@ -472,7 +472,7 @@ impl Response {
     ///
     /// Only returns something if [`Self::contains_pointer`] is true,
     /// the user is drag-dropping something of this type,
-    /// and they released it this frame
+    /// and they released it this frame.
     #[doc(alias = "drag and drop")]
     pub fn dnd_release_payload<Payload: Any + Send + Sync>(&self) -> Option<Arc<Payload>> {
         // NOTE: we use `response.contains_pointer` here instead of `hovered`, because

crates/egui/src/ui.rs

@@ -3011,7 +3011,7 @@ impl Ui {
     ///
     /// Returns the dropped item, if it was released this frame.
     ///
-    /// The given frame is used for its margins, but it color is ignored.
+    /// The given frame is used for its margins, but the color is ignored.
     #[doc(alias = "drag and drop")]
     pub fn dnd_drop_zone<Payload, R>(
         &mut self,