add test for relative purge path resolution in JIT mode

Author: bradlc

tests/jit/relative-purge-paths.config.js

@@ -0,0 +1,7 @@
+module.exports = {
+  mode: 'jit',
+  purge: ['./relative-purge-paths.test.html'],
+  corePlugins: { preflight: false },
+  theme: {},
+  plugins: [],
+}