Update states-vulnerabilities package.size field type to unsigned_long (

#663)

* Add custom package ECS definition with package.size as unsigned_long

* Update package.size description

* Update main package ECS field description

ecs/states-vulnerabilities/fields/custom/package.yml

@@ -0,0 +1,15 @@
+- name: package
+  title: Package
+  group: 2
+  short: These fields contain information about an installed software package.
+  description: >
+    These fields contain information about an installed software package.
+    It contains general information about a package, such as name, version or size.
+    It also contains installation details, such as time or location.
+  type: group
+  fields:
+    - name: size
+      type: unsigned_long
+      level: custom
+      description: >
+        Package size in bytes.