fix(grammar): make brace and keyword separately queryable

test/corpus/blocks.txt

@@ -9,8 +9,10 @@ Simple block
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name))
   (block_close
+    (block_keyword)
     (block_name))
   (content))
 
@@ -25,12 +27,14 @@ Block with content
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name))
   (content)
   (variable
     (variable_name))
   (content)
   (block_close
+    (block_keyword)
     (block_name))
   (content))
 
@@ -45,14 +49,18 @@ Nested blocks
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name))
   (block_open
+    (block_keyword)
     (block_name))
   (variable
     (variable_name))
   (block_close
+    (block_keyword)
     (block_name))
   (block_close
+    (block_keyword)
     (block_name))
   (content))
 
@@ -67,6 +75,7 @@ Block with one attribute
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name)
     (attributes
       (attribute
@@ -75,6 +84,7 @@ Block with one attribute
   (variable
     (variable_name))
   (block_close
+    (block_keyword)
     (block_name))
   (content))
 
@@ -89,6 +99,7 @@ Block with multiple attributes
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name)
     (attributes
       (attribute
@@ -98,6 +109,7 @@ Block with multiple attributes
         (attribute_name)
         (attribute_value))))
   (block_close
+    (block_keyword)
     (block_name))
   (content))
 
@@ -112,8 +124,10 @@ Case insensitive block keyword
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name))
   (block_close
+    (block_keyword)
     (block_name))
   (content))
 
@@ -128,12 +142,16 @@ Conditional block
 (template
   (content)
   (block_open
+    (block_keyword)
     (block_name))
   (block_open
+    (block_keyword)
     (block_name))
   (content)
   (block_close
+    (block_keyword)
     (block_name))
   (block_close
+    (block_keyword)
     (block_name))
   (content))