fix(package): update @angular/material to version 9.2.4

Closes #83

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "@angular/common": "^7.2.15",
     "@angular/core": "^7.2.15",
     "@angular/http": "^7.2.15",
-    "@angular/material": "^7.2.0",
+    "@angular/material": "^9.2.4",
     "@angular/platform-browser": "^7.2.15",
     "ngx-linkifyjs": "^1.2.2"
   },