Add meta-data for banner keys

Fixes gh-2093

spring-boot/src/main/java/org/springframework/boot/SpringApplication.java

@@ -468,7 +468,7 @@ public class SpringApplication {
 	/**
 	 * Print a custom banner message to the console, optionally extracting its location or
 	 * content from the Environment (banner.location and banner.charset). The defaults are
-	 * banner.location=classpath:banner.txt, banner.charest=UTF-8. If the banner file does
+	 * banner.location=classpath:banner.txt, banner.charset=UTF-8. If the banner file does
 	 * not exist or cannot be printed, a simple default is created.
 	 * @see #setShowBanner(boolean)
 	 * @see #printBanner()

spring-boot/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -4,6 +4,18 @@
     "type": "org.springframework.boot.logging.LoggingApplicationListener"
   }
 ],"properties": [
+  {
+    "name": "banner.charset",
+    "type": "java.nio.charset.Charset",
+    "description": "Banner file encoding.",
+    "defaultValue": "UTF-8"
+  },
+  {
+    "name": "banner.location",
+    "type": "java.lang.String",
+    "description": "Banner file location.",
+    "defaultValue": "classpath:banner.txt"
+  },
   {
     "name": "debug",
     "type": "java.lang.Boolean",