Improve ASP.NET Core docs and reference NuGet library

[erwinkramer]

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Description

This PR:

• Fixes the UseJsonSerializationOptions reference to use the right value. UseJsonSerializerOptions doesn't exist (anymore).
• Makes it clear what is library is required for dependency injection on ASP.NET Core.
• Small doc formatting

[nelson-parente]

Pre-review for @marcduiker handoff: LGTM with nits.

• Fixes UseJsonSerializerOptions → UseJsonSerializationOptions (correct method name) — this is an actual bug fix, good catch.
• Adds NuGet install step for Dapr.AspNetCore before the DI usage examples — helpful for newcomers.
• Trailing whitespace removals are cosmetic, no concern.
• Nit: the PR branch is named v1.17 but targets main — double-check if this is a backport or a main-branch update; if it's main-only the branch name is misleading but harmless.
  Nothing blocking — Marc, your call.