feat: builds a way to inject custom React providers into admin UI

* fix: rich text textarea height

* feat: custom providers for admin panel

* docs: custom provider component

src/admin/components/forms/field-types/RichText/RichText.tsx

@@ -272,6 +272,7 @@ const RichText: React.FC<Props> = (props) => {
               ref={editorRef}
             >
               <Editable
+                className={`${baseClass}__input`}
                 renderElement={renderElement}
                 renderLeaf={renderLeaf}
                 placeholder={placeholder}

src/admin/components/forms/field-types/RichText/index.scss

@@ -17,7 +17,6 @@
   }
 
   &__editor {
-    min-height: base(10);
 
     [data-slate-node=element] {
       margin-bottom: base(0.25);
@@ -31,6 +30,10 @@
     }
   }
 
+  &__input {
+    min-height: base(10);
+  }
+
   &__wrap {
     width: 100%;
     position: relative;