Clarify the behavior when the notation comment includes other contents

[sapphi-red]

The spec does not clarify whether other contents can be contained in the notation comments.

/* a #__PURE__ */ foo()

Input	terser	Rollup	esbuild	SWC	Oxc
/* a #__PURE__ */ foo()	✅	✅	✅	❌	❌
/* a#__PURE__ */ foo()	✅	✅	✅	❌	❌
/* #__PURE__a */ foo()	✅	✅	❌	❌	✅
/* #__PURE__ a */ foo()	✅	✅	✅	❌	✅

✅: treated as notation comments
❌: not treated as notation comments

Currently, the behavior is not aligned.