Allow lang without quotes and lang="typescript"

<script lang=ts> and <style lang=sass> without quotes weren't
recognized, so they used the first syntax in the config. For sass, it
also flattened the nesting when indenting. lang="typescript" wasn't
recognized either.

Languages not in the config still use the first syntax as before.

test/cases/lang-attr.vue

@@ -0,0 +1,20 @@
+<template lang=html>
+  <div>x</div>
+</template>
+
+<script lang=ts>
+let a: number = 1
+</script>
+
+<script lang="typescript">
+let b: number = 2
+</script>
+
+<style lang='scss'>
+$c: 1px;
+</style>
+
+<style lang=sass>
+p
+  color: red
+</style>