Improve README.md

[MixeroTN]

Motivation and Context

README.md had several visual problems, which I decided to fix.

Description

• The first problem was a dotnet-ci status badge, which is no longer available. I replaced it with two status badges: dotnet-ci-docker and dotnet-ci-windows.
• The second one was Using Semantic Kernel in C# and Python. The icons were positioned out of place. I have made a small table with the icons and hyperlinks present earlier.
• And finally, small corrections such as h3 lines for C# and Python approaches above getting started with the basics instructions.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows SK Contribution Guidelines (https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
• The code follows the .NET coding conventions (https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions) verified with dotnet format
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[MixeroTN]

@MixeroTN please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

@microsoft-github-policy-service agree [company="{your company}"]

Options:

• (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer.

@microsoft-github-policy-service agree

• (when company given) I am making Submissions in the course of work for my employer (or my employer has intellectual property rights in my Submissions by contract or applicable law). I have permission from my employer to make Submissions and enter into this Agreement on behalf of my employer. By signing below, the defined term “You” includes me and my employer.

@microsoft-github-policy-service agree company="Microsoft"

Contributor License Agreement

@microsoft-github-policy-service agree

[gitri-ms]

Thank you @MixeroTN!