Fix typo in README.md (#1660)

Author: eltociear

README.md

@@ -51,7 +51,7 @@ crowd.dev is open-source, built with developers in mind, available for both host
 
 **To our developer community:**
 - You can self-host crowd.dev to centralize data for your community or company while keeping full control over your data.
-- Our product is built for extensibilty. If you can think of any use cases that you want to build with the data we collect and store for you, please go ahead and build it! We will be here to help out if you need us.
+- Our product is built for extensibility. If you can think of any use cases that you want to build with the data we collect and store for you, please go ahead and build it! We will be here to help out if you need us.
 - You can actively contribute to crowd.dev (e.g. integrations), and we will be supporting you along the journey. Just take a look at our [Contributing guide](https://github.com/CrowdDotDev/crowd.dev/blob/main/CONTRIBUTING.md).
 
 ## ✨ Features