gpui: Add align-self methods to Styled trait (#51652)

This PR adds the missing methods for the `align-self` css property. The
`align_self` field existed on the `StyleRefinement` struct but was
inaccessible using the `styled` trait.

Release Notes:

- Adds `self_start`, `self_end`, `self_center`, `self_flex_start`,
`self_flex_end`, `self_baseline`, and `self_stretch` methods to the
`trait Styled`

crates/gpui/src/styled.rs

@@ -1,5 +1,5 @@
 use crate::{
-    self as gpui, AbsoluteLength, AlignContent, AlignItems, BorderStyle, CursorStyle,
+    self as gpui, AbsoluteLength, AlignContent, AlignItems, AlignSelf, BorderStyle, CursorStyle,
     DefiniteLength, Display, Fill, FlexDirection, FlexWrap, Font, FontFeatures, FontStyle,
     FontWeight, GridPlacement, Hsla, JustifyContent, Length, SharedString, StrikethroughStyle,
     StyleRefinement, TextAlign, TextOverflow, TextStyleRefinement, UnderlineStyle, WhiteSpace, px,
@@ -278,6 +278,55 @@ pub trait Styled: Sized {
         self
     }
 
+    /// Sets how this specific element is aligned along the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#start)
+    fn self_start(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::Start);
+        self
+    }
+
+    /// Sets this element to align against the end of the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#end)
+    fn self_end(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::End);
+        self
+    }
+
+    /// Sets this element to align against the start of the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#start)
+    fn self_flex_start(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::FlexStart);
+        self
+    }
+
+    /// Sets this element to align against the end of the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#end)
+    fn self_flex_end(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::FlexEnd);
+        self
+    }
+
+    /// Sets this element to align along the center of the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#center)
+    fn self_center(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::Center);
+        self
+    }
+
+    /// Sets this element to align along the baseline of the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#baseline)
+    fn self_baseline(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::Baseline);
+        self
+    }
+
+    /// Sets this element to stretch to fill the available space along the container's cross axis.
+    /// [Docs](https://tailwindcss.com/docs/align-self#stretch)
+    fn self_stretch(mut self) -> Self {
+        self.style().align_self = Some(AlignSelf::Stretch);
+        self
+    }
+
     /// Sets the element to justify flex items against the start of the container's main axis.
     /// [Docs](https://tailwindcss.com/docs/justify-content#start)
     fn justify_start(mut self) -> Self {