add grid_gap e2e test

e2etests/stable_test.go

@@ -2572,6 +2572,7 @@ scenarios: {
 		loadFromFile(t, "grid_tests"),
 		loadFromFile(t, "executive_grid"),
 		loadFromFile(t, "grid_animated"),
+		loadFromFile(t, "grid_gap"),
 	}
 
 	runa(t, tcs)

e2etests/testdata/files/grid_gap.d2

@@ -0,0 +1,66 @@
+gap-rows 30 gap-columns 100: {
+  grid-rows: 3
+  grid-columns: 3
+  grid-gap-rows: 30
+  grid-gap-columns: 100
+
+  a
+  b
+  c
+  d
+  e
+  f
+  g
+  h
+  i
+}
+
+gap-rows 100 gap-columns 30: {
+  grid-rows: 3
+  grid-columns: 3
+  grid-gap-rows: 100
+  grid-gap-columns: 30
+
+  a
+  b
+  c
+  d
+  e
+  f
+  g
+  h
+  i
+}
+
+gap 0: {
+  grid-rows: 3
+  grid-columns: 3
+  grid-gap: 0
+
+  a
+  b
+  c
+  d
+  e
+  f
+  g
+  h
+  i
+}
+
+gap 10 gap-rows 100: {
+  grid-rows: 3
+  grid-columns: 3
+  grid-gap: 10
+  grid-gap-rows: 100
+
+  a
+  b
+  c
+  d
+  e
+  f
+  g
+  h
+  i
+}