Update: add LICENSE-material-design (#3922)

* Update: add LICENSE-material-design

LICENSE

@@ -222,8 +222,8 @@ The text of each license is the standard Apache 2.0 license.
    proto files from lyft/protoc-gen-validate: https://github.com/lyft/protoc-gen-validate Apache 2.0
    proto files from gogo/googleapis: https://github.com/gogo/googleapis Apache 2.0
    mvnw files from https://github.com/takari/maven-wrapper Apache 2.0
-
-
+   svg files from skywalking-ui/src/assets/icons: https://github.com/google/material-design-icons Apache 2.0
+    
 ========================================================================
 BSD licenses
 ========================================================================

apm-dist/release-docs/LICENSE

@@ -423,7 +423,7 @@ lodash	4.17.15:	https://github.com/lodash/lodash	MIT
 Apache 2.0 licenses
 ========================================
 echarts	4.1.0:	https://github.com/apache/incubator-echarts	Apache-2.0
-
+Material Icons 3.0.1 https://github.com/google/material-design-icons Apache-2.0
 ========================================
 BSD licenses
 ========================================