Fix heading styles + Added style test

Author: tingerrr

src/style.typ

@@ -58,6 +58,7 @@
       block({
         if it.numbering != none {
           text(fill: theme.colors.primary, counter(heading).display())
+          [ ]
         }
         it.body
       })

tests/complete/ref/1.png

@@ -0,0 +1 @@
+# added by typst-test

tests/style/.gitignore

@@ -0,0 +1,19 @@
+#import "/src/style.typ"
+
+#show: style.default()
+
+= First Part
+#lorem(100)
+
+= Second Part
+#lorem(50)
+
+== Section
+== Another Section
+#lorem(250)
+
+=== Subsection
+#lorem(100)
+
+= Third Part
+#lorem(250)