Added PR stop notice (#3532)

README.md

@@ -13,6 +13,15 @@ You can learn more on [prismjs.com](https://prismjs.com/).
 
 ## Contribute to Prism!
 
+### **Important Notice**
+
+We are currently working on [Prism v2](https://github.com/PrismJS/prism/discussions/3531) and will only accept security-relevant PRs for the time being.
+
+Once work on Prism v2 is sufficiently advanced, we will accept PRs again. This will be announced on our [Discussion](https://github.com/PrismJS/prism/discussions) page and mentioned in the [roadmap discussion](https://github.com/PrismJS/prism/discussions/3531).
+
+<details>
+<summary>Prism v1 contributing notes</summary>
+
 Prism depends on community contributions to expand and cover a wider array of use cases. If you like it, consider giving back by sending a pull request. Here are a few tips:
 
 - Read the [documentation](https://prismjs.com/extending.html). Prism was designed to be extensible.
@@ -35,6 +44,8 @@ Prism will run on [almost any browser](https://prismjs.com/#features-full) and N
 - Node.js >= 10.x
 - npm >= 6.x
 
+</details>
+
 ## Translations
 
 * [简体中文](https://www.awesomes.cn/repo/PrismJS/prism) (if unavailable, see [here](https://deepmind.t-salon.cc/article/113))

docs/index.html

@@ -59,6 +59,11 @@ <h2><a href="index.html">Home</a></h2><h2><a href="https://prismjs.com" class="m
 <p><a href="https://lea.verou.me/2012/07/introducing-prism-an-awesome-new-syntax-highlighter/#more-1841">Why another syntax highlighter?</a></p>
 <p><a href="https://github.com/PrismJS/prism-themes">More themes for Prism!</a></p>
 <h2>Contribute to Prism!</h2>
+<h3><strong>Important Notice</strong></h3>
+<p>We are currently working on <a href="https://github.com/PrismJS/prism/discussions/3531">Prism v2</a> and will only accept security-relevant PRs for the time being.</p>
+<p>Once work on Prism v2 is sufficiently advanced, we will accept PRs again. This will be announced on our <a href="https://github.com/PrismJS/prism/discussions">Discussion</a> page and mentioned in the <a href="https://github.com/PrismJS/prism/discussions/3531">roadmap discussion</a>.</p>
+<details>
+<summary>Prism v1 contributing notes</summary>
 <p>Prism depends on community contributions to expand and cover a wider array of use cases. If you like it, consider giving back by sending a pull request. Here are a few tips:</p>
 <ul>
 <li>Read the <a href="https://prismjs.com/extending.html">documentation</a>. Prism was designed to be extensible.</li>
@@ -79,6 +84,7 @@ <h3>Software requirements</h3>
 <li>Node.js &gt;= 10.x</li>
 <li>npm &gt;= 6.x</li>
 </ul>
+</details>
 <h2>Translations</h2>
 <ul>
 <li><a href="https://www.awesomes.cn/repo/PrismJS/prism">简体中文</a> (if unavailable, see <a href="https://deepmind.t-salon.cc/article/113">here</a>)</li>