change heading font weight

h1 and h2 : Semi Bold (600)
- 376cac43a0/resources/assets/less/bem/osu-md.less (L111)
- 376cac43a0/resources/assets/less/bem/osu-md.less (L135)

The rest of heading : Bold (700)
- 376cac43a0/resources/assets/less/bem/osu-md.less (L97)

osu.Game/Graphics/Containers/Markdown/OsuMarkdownHeading.cs

@@ -3,16 +3,25 @@
 
 using Markdig.Syntax;
 using osu.Framework.Graphics.Containers.Markdown;
+using osu.Framework.Graphics.Sprites;
 
 namespace osu.Game.Graphics.Containers.Markdown
 {
     public class OsuMarkdownHeading : MarkdownHeading
     {
+        private readonly int level;
+
         public OsuMarkdownHeading(HeadingBlock headingBlock)
             : base(headingBlock)
         {
+            level = headingBlock.Level;
         }
 
+        public override MarkdownTextFlowContainer CreateTextFlow() => new HeadingTextFlowContainer
+        {
+            Weight = GetFontWeightByLevel(level),
+        };
+
         protected override float GetFontSizeByLevel(int level)
         {
             const float base_font_size = 14;
@@ -38,5 +47,30 @@ protected override float GetFontSizeByLevel(int level)
                     return 1;
             }
         }
+
+        protected virtual FontWeight GetFontWeightByLevel(int level)
+        {
+            switch (level)
+            {
+                case 1:
+                case 2:
+                    return FontWeight.SemiBold;
+
+                default:
+                    return FontWeight.Bold;
+            }
+        }
+
+        private class HeadingTextFlowContainer : OsuMarkdownTextFlowContainer
+        {
+            public FontWeight Weight { get; set; }
+
+            protected override SpriteText CreateSpriteText()
+            {
+                var spriteText = base.CreateSpriteText();
+                spriteText.Font = spriteText.Font.With(weight: Weight);
+                return spriteText;
+            }
+        }
     }
 }