feat: add inner left/right support. add max box height.

demo/Ursa.Demo/Pages/MultiComboBoxDemo.axaml

@@ -1,15 +1,23 @@
-<UserControl xmlns="https://github.com/avaloniaui"
-             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
-             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
-             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
-             xmlns:vm="using:Ursa.Demo.ViewModels"
-             xmlns:u="https://irihi.tech/ursa"
-             x:DataType="vm:MultiComboBoxDemoViewModel"
-             x:CompileBindings="True"
-             x:Class="Ursa.Demo.Pages.MultiComboBoxDemo">
+<UserControl
+    x:Class="Ursa.Demo.Pages.MultiComboBoxDemo"
+    xmlns="https://github.com/avaloniaui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:u="https://irihi.tech/ursa"
+    xmlns:vm="using:Ursa.Demo.ViewModels"
+    d:DesignHeight="450"
+    d:DesignWidth="800"
+    x:CompileBindings="True"
+    x:DataType="vm:MultiComboBoxDemoViewModel"
+    mc:Ignorable="d">
     <StackPanel Orientation="Horizontal">
-        <u:MultiComboBox Classes="ClearButton" Name="combo" ItemsSource="{Binding Items}"/>
-        <ListBox ItemsSource="{Binding #combo.SelectedItems}"/>
+        <u:MultiComboBox
+            Name="combo"
+            InnerLeftContent="Left"
+            InnerRightContent="Right"
+            Classes="ClearButton"
+            ItemsSource="{Binding Items}" />
+        <ListBox ItemsSource="{Binding #combo.SelectedItems}" />
     </StackPanel>
 </UserControl>

demo/Ursa.Demo/ViewModels/MultiComboBoxDemoViewModel.cs

@@ -25,6 +25,27 @@ public class MultiComboBoxDemoViewModel: ObservableObject
             "Kansas",
             "Kentucky",
             "Louisiana",
+            "Maine",
+            "Maryland",
+            "Massachusetts",
+            "Michigan",
+            "Minnesota",
+            "Mississippi",
+            "Missouri",
+            "Montana",
+            "Nebraska",
+            "Nevada",
+            "New Hampshire",
+            "New Jersey",
+            "New Mexico",
+            "New York",
+            "North Carolina",
+            "North Dakota",
+            "Ohio",
+            "Oklahoma",
+            "Oregon",
+            "Pennsylvania",
+            "Rhode Island",
         };
     }
 }