Marks a Proposed Recommendation as intending to allow new features once it becomes a W3C Recommendation. ReSpec adds the required boilerplate text automatically.

<section id="sotd" class="updateable-rec">
  <p>This specification may be amended by adding new features
  in future levels.</p>
</section>

• Only relevant for "PR" (Proposed Recommendation) documents heading toward "REC"
• Enables the W3C Process 2020 mechanism for publishing updated Recommendations
• ReSpec validates consistency between specStatus and this class