Dotnet fsi dependencymanager extensions doc (#10511)

Co-authored-by: Phillip Carter <[email protected]>

src/fsharp/FSharp.DependencyManager.Nuget/README.md

@@ -0,0 +1,17 @@
+# `dotnet fsi`: NuGet Dependency Manager Plugin
+
+This extension ships by default since .NET 5. It can be used in F# interactive through `dotnet fsi` without further setup through `#r "nuget:"` references.
+
+```fsharp
+#r "nuget: Newtonsoft.Json"
+// Optionally, specify a version explicitly
+// #r "nuget: Newtonsoft.Json,11.0.1"
+
+open Newtonsoft.Json
+
+let o = {| X = 2; Y = "Hello" |}
+
+printfn "%s" (JsonConvert.SerializeObject o)"
+```
+
+There are more Dependency Manager extensions, find more about them: [Microsoft.DotNet.DependencyManager](https://github.com/dotnet/fsharp/tree/main/src/fsharp/Microsoft.DotNet.DependencyManager)

src/fsharp/Microsoft.DotNet.DependencyManager/README.md

@@ -0,0 +1,44 @@
+# `dotnet fsi` Dependency Manager Plugins
+
+Since .NET 5.0, `dotnet fsi` ships with dependency manager plugins support that can be called like so:
+
+```fsharp
+#r "myextension: my extension parameters"
+```
+
+# `#r "nuget:"` [nuget](https://github.com/dotnet/fsharp/tree/main/src/fsharp/FSharp.DependencyManager.Nuget)
+
+Reference nuget packages, ships by default with `dotnet fsi`.
+
+```fsharp
+#r "nuget: Newtonsoft.Json"
+// Optionally, specify a version explicitly
+// #r "nuget: Newtonsoft.Json,11.0.1"
+
+open Newtonsoft.Json
+
+let o = {| X = 2; Y = "Hello" |}
+
+printfn "%s" (JsonConvert.SerializeObject o)
+```
+
+# `#r "paket:"` [paket](https://fsprojects.github.io/Paket/fsi-integration.html)
+
+Reference dependencies (nuget, git, gist, github) through [Paket package manager](https://fsprojects.github.io/Paket).
+
+Learn how to use [Paket FSI integration](https://fsprojects.github.io/Paket/fsi-integration.html).
+
+```fsharp
+#r "paket: nuget FSharp.Data"
+
+open FSharp.Data
+
+type MyCsv = CsvProvider<"""
+X,Y
+2,Hello
+4,World
+""">
+
+for r in MyCsv.GetSample().Rows do
+  printfn "%i = %s" r.X r.Y
+```