Update README.md (#45920)

Changed the headings to sentence-case for consistency and style reasons.

Author: ivancheban

README.md

@@ -7,15 +7,15 @@ ASP.NET Core
 
 ASP.NET Core is an open-source and cross-platform framework for building modern cloud-based internet-connected applications, such as web apps, IoT apps and mobile backends. ASP.NET Core apps run on [.NET](https://dot.net), a free, cross-platform and open-source application runtime. It was architected to provide an optimized development framework for apps that are deployed to the cloud or run on-premises. It consists of modular components with minimal overhead, so you retain flexibility while constructing your solutions. You can develop and run your ASP.NET Core apps cross-platform on Windows, Mac and Linux. [Learn more about ASP.NET Core](https://docs.microsoft.com/aspnet/core/).
 
-## Get Started
+## Get started
 
 Follow the [Getting Started](https://docs.microsoft.com/aspnet/core/getting-started) instructions in the [ASP.NET Core docs](https://docs.microsoft.com/aspnet/index).
 
 Also check out the [.NET Homepage](https://www.microsoft.com/net) for released versions of .NET, getting started guides, and learning resources.
 
 See the [Triage Process](https://github.com/dotnet/aspnetcore/blob/main/docs/TriageProcess.md) document for more information on how we handle incoming issues.
 
-## How to Engage, Contribute, and Give Feedback
+## How to engage, contribute, and give feedback
 
 Some of the best ways to contribute are to try things out, file issues, join in design conversations,
 and make pull-requests.