feat: tumblr grammar with highlights, injections, and tests

test/corpus/variables.txt

@@ -0,0 +1,103 @@
+==================
+Plain variable
+==================
+
+{Title}
+
+---
+
+(template
+  (content)
+  (variable
+    (variable_name))
+  (content))
+
+==================
+Variable with numeric size suffix
+==================
+
+{PortraitURL-128}
+
+---
+
+(template
+  (content)
+  (variable
+    (variable_name)
+    (variable_modifier))
+  (content))
+
+==================
+Variable with named size suffix
+==================
+
+{PhotoURL-HighRes}
+
+---
+
+(template
+  (content)
+  (variable
+    (variable_name)
+    (variable_modifier))
+  (content))
+
+==================
+Multiple variables with text between
+==================
+
+<h1>{Title}</h1>
+<p>{Description}</p>
+
+---
+
+(template
+  (content)
+  (variable
+    (variable_name))
+  (content)
+  (variable
+    (variable_name))
+  (content))
+
+==================
+Prefixed variable
+==================
+
+{color:Background} {font:Body} {image:Header} {text:Tagline}
+
+---
+
+(template
+  (content)
+  (variable
+    (variable_prefix)
+    (prefix_argument))
+  (content)
+  (variable
+    (variable_prefix)
+    (prefix_argument))
+  (content)
+  (variable
+    (variable_prefix)
+    (prefix_argument))
+  (content)
+  (variable
+    (variable_prefix)
+    (prefix_argument))
+  (content))
+
+==================
+Prefix argument with spaces
+==================
+
+{text:Header Subtitle}
+
+---
+
+(template
+  (content)
+  (variable
+    (variable_prefix)
+    (prefix_argument))
+  (content))