Merge pull request #753 from sgbett/fix/752-stack-length

fix(script): add length/size to Stack (#752)

Author: sgbett

gem/bsv-sdk/lib/bsv/script/interpreter/stack.rb

@@ -98,6 +98,9 @@ def depth
         @items.length
       end
 
+      alias length depth
+      alias size depth
+
       def empty?
         @items.empty?
       end