fixed extensions.md

docs/extensions.md

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+# Extensions
+
+## #gallery
+
+## Using Extensions
+
+In the web editor, click on ``Settings`` then ``Extensions`` to search and add extensions to the project.
+The Blocks and JavaScript definitions will be automatically loaded in the editor.
+
+## Custom extensions
+
+The [Build Your Own Extension](https://makecode.com/extensions/getting-started) manual is for advanced users who want to publish their own extension. 
+
+## ~ hint
+
+**Extensions** were previously called **Packages** in MakeCode.
+
+## ~