Add init keyword (#23422)

Author: tdykstra

docs/csharp/language-reference/keywords/index.md

@@ -50,14 +50,14 @@ Keywords are predefined, reserved identifiers that have special meanings to the
 |[async](async.md)|[await](../operators/await.md)|[by](by.md)|
 |[descending](descending.md)|[dynamic](../builtin-types/reference-types.md)|[equals](equals.md)|
 |[from](from-clause.md)|[get](get.md)|[global](../operators/namespace-alias-qualifier.md)|
-|[group](group-clause.md)|[into](into.md)|[join](join-clause.md)|
-|[let](let-clause.md)|[nameof](../operators/nameof.md)|[nint](../builtin-types/nint-nuint.md)|
-|[notnull](../../programming-guide/generics/constraints-on-type-parameters.md#notnull-constraint)|[nuint](../builtin-types/nint-nuint.md)|[on](on.md)|
-|[orderby](orderby-clause.md)|[partial (type)](partial-type.md)|[partial (method)](partial-method.md)|
-|[remove](remove.md)|[select](select-clause.md)|[set](set.md)|
-|[unmanaged (generic type constraint)](../../programming-guide/generics/constraints-on-type-parameters.md#unmanaged-constraint)|[value](value.md)|[var](var.md)|
-|[when (filter condition)](when.md)|[where (generic type constraint)](where-generic-type-constraint.md)|[where (query clause)](where-clause.md)|
-|[with](../operators/with-expression.md)|[yield](yield.md)||
+|[group](group-clause.md)|[init](init.md)|[into](into.md)|
+|[join](join-clause.md)|[let](let-clause.md)|[nameof](../operators/nameof.md)|
+|[nint](../builtin-types/nint-nuint.md)|[notnull](../../programming-guide/generics/constraints-on-type-parameters.md#notnull-constraint)|[nuint](../builtin-types/nint-nuint.md)|
+|[on](on.md)|[orderby](orderby-clause.md)|[partial (type)](partial-type.md)|
+|[partial (method)](partial-method.md)|[remove](remove.md)|[select](select-clause.md)|
+|[set](set.md)|[unmanaged (generic type constraint)](../../programming-guide/generics/constraints-on-type-parameters.md#unmanaged-constraint)|[value](value.md)|
+|[var](var.md)|[when (filter condition)](when.md)|[where (generic type constraint)](where-generic-type-constraint.md)|
+|[where (query clause)](where-clause.md)|[with](../operators/with-expression.md)|[yield](yield.md)||
 
 ## See also