`dotnet-upgrade/.../migrate-dotnet*` skills are missing F# vs. C#

The `migrate-dotnet*` skills are missing F# differentiation. The skills are written C# focused rather than being generic .NET skills.

Examples:

```diff
-| Project or solution path | Yes | The `.csproj`, `.sln`, or `.slnx` entry point to migrate |
+| Project or solution path | Yes | The `.csproj`, `.fsproj`, `.sln`, or `.slnx` entry point to migrate |
```

```diff
-1. In each `.csproj` (or `Directory.Build.props` if centralized), change:
+1. In each `.csproj`/`.fsproj` (or `Directory.Build.props` if centralized), change:
```

```diff
-| `references/csharp-compiler-dotnet9to10.md` | Always (C# 14 compiler breaking changes) |
+| `references/csharp-compiler-dotnet9to10.md` | Project uses C# (C# 14 compiler breaking changes) |
+| `references/fsharp-compiler-dotnet9to10.md` | Project uses F# (F# 10 compiler breaking changes) |
```

A few minor tweaks like this and the skills will be useful in both C#, F#, and mixed solutions.