fix: HyberLink uss unity 2018 support

Author: stan-osipov

Editor/Core/FoundationPackage.cs

@@ -18,7 +18,7 @@ public static class FoundationPackage
         public static readonly string RootPath = PackageManagerUtility.GetPackageRootPath(Name);
 
 
-#if UNITY_2019_1_OR_NEWER
+#if UNITY_2019_4_OR_NEWER
         /// <summary>
         /// Foundation package info.
         /// </summary>

Editor/EditorUtilities/PackageManagerUtility.cs

@@ -18,7 +18,7 @@ public static class PackageManagerUtility
         /// </summary>
         public const string ManifestPath = "Packages/manifest.json";
 
-#if UNITY_2019_1_OR_NEWER
+#if UNITY_2019_4_OR_NEWER
         /// <summary>
         /// Returns PackageInfo if package is installed in the project, <c>null</c> otherwise.
         /// </summary>

Editor/EditorUtilities/UIToolkitEditorUtility.cs

@@ -1,4 +1,4 @@
-#if UNITY_2019_1_OR_NEWER
+#if UNITY_2019_4_OR_NEWER
 using System;
 using UnityEditor;
 using UnityEngine;

Editor/UIToolkit/Controls/ButtonStrip/ButtonStrip.cs

@@ -1,4 +1,4 @@
-#if UNITY_2019_1_OR_NEWER
+#if UNITY_2019_4_OR_NEWER
 using System;
 using System.Collections.Generic;
 using System.Linq;

Editor/UIToolkit/Controls/HelpBox/HelpBox.cs

@@ -1,4 +1,4 @@
-#if UNITY_2019_1_OR_NEWER
+#if UNITY_2019_4_OR_NEWER
 using JetBrains.Annotations;
 using UnityEditor;
 using UnityEngine.UIElements;

Editor/UIToolkit/Controls/Hyperlink/Hyperlink.cs

@@ -1,4 +1,5 @@
-using JetBrains.Annotations;
+#if UNITY_2019_4_OR_NEWER
+using JetBrains.Annotations;
 using StansAssets.Foundation.Editor;
 using UnityEngine;
 using UnityEngine.UIElements;
@@ -60,4 +61,5 @@ public Hyperlink()
             UIToolkitEditorUtility.ApplyStyleForInternalControl(this, nameof(Hyperlink));
         }
     }
-}
+}
+#endif

Editor/UIToolkit/Controls/Hyperlink/Hyperlink.uss

@@ -8,7 +8,7 @@
 .stansassets-settings-block__header {
     margin-top: 5px;
     margin-bottom: 5px;
-    font-size: 13;
+    font-size: 13px;
     -unity-font-style: bold;
 }