minor #18385 [AssetMapper] Update asset_mapper.rst (phiali)

This PR was merged into the 6.3 branch.

Discussion
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[AssetMapper] Update asset_mapper.rst

This corrects a grammatical error

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Commits
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e4c2654 Update asset_mapper.rst

Author: javiereguiluz

frontend/asset_mapper.rst

@@ -721,7 +721,7 @@ First, install the ``tailwindcss`` binary. This can be installed via npm (run
 
     $ npm install -D tailwindcss
 
-Of you can install the `Tailwind standalone binary`_, which does not require Node.
+Or you can install the `Tailwind standalone binary`_, which does not require Node.
 
 Next, generate the ``tailwind.config.js`` file: