Update v9-feature-tracker.md (#1354)

Author: RexJaeschke

admin/v9-feature-tracker.md

@@ -26,4 +26,8 @@ Attributes and extern on local functions ([MS Proposal](https://github.com/dotne
 Module initializers ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/module-initializers.md))	| [992](https://github.com/dotnet/csharpstandard/pull/992)| SPEC'D | small | Done |
 New features for partial methods ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/extending-partial-methods.md))	| [991](https://github.com/dotnet/csharpstandard/pull/991) | SPEC'D | small | Done | 
 Target-typed new expressions ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/target-typed-new.md))	| [990](https://github.com/dotnet/csharpstandard/pull/990) | SPEC'D | small | N/A |
-Unconstrained type parameter annotations ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/unconstrained-type-parameter-annotations.md))	| [1326](https://github.com/dotnet/csharpstandard/pull/1326)| SPEC'D | small | N/A | 
+Unconstrained type parameter annotations ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/unconstrained-type-parameter-annotations.md))	| [1326](https://github.com/dotnet/csharpstandard/pull/1326) | SPEC'D | small | N/A | 
+Variance safety for static interface members ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/variance-safety-for-static-interface-members.md))	| [1343](https://github.com/dotnet/csharpstandard/pull/1343) | SPEC'D | small | N/A | 
+Nullable reference types ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/nullable-reference-types-specification.md))	| [1221](https://github.com/dotnet/csharpstandard/pull/1221)| SPEC'D | small | Done | The `default` constraint part is handled by PR #[1326](https://github.com/dotnet/csharpstandard/pull/1326)
+Nullable constructor analysis ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/nullable-constructor-analysis.md))	| None | | | | Contains implementation details only; no spec changes necessary
+Nullable parameter default value analysis ([MS Proposal](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-9.0/nullable-parameter-default-value-analysis.md))	| None | | | | Contains implementation details only; no spec changes necessary