Repository: nodejs/node
Pull request: doc: fix stability 1.x links excluding the decimal digit

Pretty minor, this is just addressing a minimal UI quirk I noticed with the `Stability 1.x` links where the decimal digits are not included in the hyperlink

PS: I've also moved the regex outside of the `preprocessElements` function, as there is no reason/benefit to have the regex rebuilt for every file (having it outside might save some precious nanoseconds when building the docs :sweat_smile:).

## Before
![before](https://github.com/user-attachments/assets/9b6a12e8-70c2-474f-bb20-71922b53edd2) 

## After
 ![after](https://github.com/user-attachments/assets/2cf09f1d-254b-404b-a620-81d79ad9543d) 



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Changed files:
filename: tools/doc/html.mjs
patch: @@ -206,10 +206,11 @@ function linkJsTypeDocs(text) {
 
 const isJSFlavorSnippet = (node) => node.lang === 'cjs' || node.lang === 'mjs';
 
+const STABILITY_RE = /(.*:)\s*(\d(?:\.\d)?)([\s\S]*)/;
+
 // Preprocess headers, stability blockquotes, and YAML blocks.
 export function preprocessElements({ filename }) {
   return (tree) => {
-    const STABILITY_RE = /(.*:)\s*(\d)([\s\S]*)/;
     let headingIndex = -1;
     let heading = null;
 
@@ -325,7 +326,7 @@ export function preprocessElements({ filename }) {
           // Insert div with prefix and number
           node.children.unshift({
             type: 'html',
-            value: `<div class="api_stability api_stability_${number}">` +
+            value: `<div class="api_stability api_stability_${parseInt(number)}">` +
               (noLinking ? '' :
                 '<a href="documentation.html#stability-index">') +
               `${prefix} ${number}${noLinking ? '' : '</a>'}`