add alias for "blankIfNull"

src/clj_jtwig/standard_functions.clj

@@ -13,7 +13,8 @@
 (defonce standard-functions
   {"blankIfNull"
    {:fn (fn [x]
-          (if (nil? x) "" x))}
+          (if (nil? x) "" x))
+    :aliases ["nonull"]}
 
    "butlast"
    {:fn (fn [sequence]

test/clj_jtwig/functions_test.clj

@@ -250,7 +250,9 @@
     (is (= (render "{{ a|blankIfNull }}" {:a nil})
            ""))
     (is (= (render "{{ a|blankIfNull }}" {:a "foo"})
-           "foo")))
+           "foo"))
+    (is (= (render "{{ a|nonull }}" nil)
+           "")))
 
   (testing "butlast"
     (is (= (render "{{ [1, 2, 3, 4, 5]|butlast }}" nil)