fmt: Add support for block nesting. (#3105)

Previously the formatter did not include support for
blocks inside other blocks. Hence the formatter could
not indent some files properly. This fixes it.

Fixes #3104

Signed-off-by: Vaibhav <vrongmeal@gmail.com>

caddyconfig/caddyfile/formatter_test.go

@@ -29,6 +29,22 @@ b
 
 e { f
 }
+
+g {
+h {
+i
+}
+}
+
+j { k {
+l
+}
+}
+
+m {
+	n { o
+	}
+}
 `)
 	expected := []byte(`
 a
@@ -41,6 +57,24 @@ c {
 e {
 	f
 }
+
+g {
+	h {
+		i
+	}
+}
+
+j {
+	k {
+		l
+	}
+}
+
+m {
+	n {
+		o
+	}
+}
 `)
 	testFormat(t, input, expected)
 }