Sample code snippet and introduction for the fslab website

Hi there, awesome work on this library!

As I will be talking about FsLab next week at .NET Conf: Focus on F#, there might be some new traffic on that page, therefore I extended the introduction parts (click on read more) of the libraries I maintain with some more introductory text and simple code snippets.

The [packages page](https://fslab.org/packages.html) contains flips as well as a part of the fslab toolbox. If you would like to add some text/snippets, the markdown file that renders the flips card is located [here](https://github.com/fslaborg/fslaborg.github.io/blob/main/src/content/datascience-packages/deedle.md) (it has just been the project summary for the last months). [Here](https://github.com/fslaborg/fslaborg.github.io/blob/main/src/content/datascience-packages/plotly.net.md) is the same for Plotly.NET as reference.

I would say i am proficient enough in using Deedle to come up with some simple code myself, but i first wanted to ask if maybe a maintainer would like to control what exactly is presented on the website.

Cheers!

Start with src/content/datascience-packages/deedle.md and compare it with src/content/datascience-packages/plotly.net.md. Review the existing introduction and coordinate with a maintainer on the introductory text and simple F# snippets to include. Done means the Deedle package card has the agreed content and examples on fslab.org/packages.html.

Written by the indexing model from the issue text.