Adds dark mode

Fix compare int-str bug
Fix empty values error
Replace sort by attribute filter with direct order_by
additional make targets

data/development/test-empty-values/contents.lr

@@ -0,0 +1,17 @@
+name: test empty values
+---
+yield: 
+---
+ingredients: 
+---
+directions: 
+---
+date: 
+---
+difficulty: 
+---
+source: 
+---
+tags: 
+---
+time: