v1.3.23

Update docs to reflect the .NET 10 cascade (#124)

Now that the compiler hosts on and targets .NET 10:

• Update prerequisite text from ".NET 8 SDK" to ".NET 10 SDK".
• Update default target language from ".NET 8" to ".NET 10".
• Update runtime-requirement language to match what the user
  actually targets.
• Update dev-container image references from dotnet:8.0 to
  dotnet:10.0.
• Note that older targets (e.g. net8.0) still work — set
  <TargetFramework>net8.0</TargetFramework> and pin
  ghul.runtime to a 3.x release, since the 4.x line is
  net10.0-only.

Co-authored-by: ghul-coder[bot] <286450068+ghul-coder[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) noreply@anthropic.com