Fix typos in PolyfillsGenerator.cs

- Fixed some typos in comments

Author: piotrstenke

src/PolySharp.SourceGenerators/PolyfillsGenerator.cs

@@ -18,7 +18,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             context.AnalyzerConfigOptionsProvider
             .Select(GetGenerationOptions);
 
-        // Get the sequence of all avaailable types that could be generated
+        // Get the sequence of all available types that could be generated
         IncrementalValuesProvider<AvailableType> availableTypes =
             context.CompilationProvider
             .SelectMany(GetAvailableTypes);
@@ -33,7 +33,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
         // Generate source for the current type depending on current accessibility
         context.RegisterSourceOutput(generatedTypes, EmitGeneratedType);
 
-        // Get all potential type forwarded type names
+        // Get all potential forwarded type names
         IncrementalValuesProvider<string> typeForwardNames =
             context.CompilationProvider
             .SelectMany(GetCoreLibTypes);
@@ -48,4 +48,4 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
         // Generate the type forwards, if any
         context.RegisterImplementationSourceOutput(filteredTypeForwardNames, EmitTypeForwards);
     }
-}
+}