minor #18816 Replace footnote by ref (alamirault)

This PR was merged into the 6.3 branch.

Discussion
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Replace footnote by ref

Fix #18814

Footnotes are not supported by doctrine/rst-parser#181

I used same hack than https://symfony.com/doc/4.4/contributing/code/bc.html#notes

Commits
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5691435 Replace footnote by ref

Author: javiereguiluz

frontend.rst

@@ -25,14 +25,19 @@ Requires a build step?            yes                no
 Works in all browsers?            yes                yes
 Supports `Stimulus/UX`_           yes                yes
 Supports Sass/Tailwind            yes                :ref:`yes <asset-mapper-tailwind>`
-Supports React, Vue, Svelte?      yes                yes [#1]_
-Supports TypeScript               yes                no [#1]_
+Supports React, Vue, Svelte?      yes                yes :ref:`[1] <note-1>`
+Supports TypeScript               yes                no :ref:`[1] <note-1>`
 ================================  =================  ======================================================
 
-.. [#1] Using JSX (React), Vue or TypeScript with AssetMapper is possible, but you'll
-        need to use their native tools for pre-compilation. Also, some features (like
-        Vue single-file components) cannot be compiled down to pure JavaScript that can
-        be executed by a browser.
+Notes
+~~~~~
+
+.. _note-1:
+
+**[1]** Using JSX (React), Vue or TypeScript with AssetMapper is possible, but you'll
+need to use their native tools for pre-compilation. Also, some features (like
+Vue single-file components) cannot be compiled down to pure JavaScript that can
+be executed by a browser.
 
 .. _frontend-webpack-encore: