Add 'pnpm' to 'PackageManager'

Author: DemiKnight

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/TypeScriptSettings.java

@@ -635,7 +635,8 @@ public static RequiredMemberMode fromString(String s) {
 
     public enum PackageManager {
         YARN("yarn"),
-        NPM("npm");
+        NPM("npm"),
+        PNPM("pnpm");
 
         private final String command;
 
@@ -654,6 +655,9 @@ public static PackageManager fromString(String s) {
             if ("npm".equals(s)) {
                 return NPM;
             }
+            if ("pnpm".equals(s)) {
+                return PNPM;
+            }
             throw new CodegenException(String.format("Unsupported package manager: %s", s));
         }
     }