Add commented out pubspec directions to enable dartdevc mode for pub serve (#420)

I'll modify the comment in an imminent PR.

lib/generators/web_angular_data.dart

@@ -145,7 +145,9 @@ cnRfdG9fanNfc2NyaXB0X3Jld3JpdGVyOiBeMS4wLjEKICB0ZXN0OiBeMC4xMi4wCgp0cmFuc2Zv
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-cnQKLSBkYXJ0X3RvX2pzX3NjcmlwdF9yZXdyaXRlcgo=""",
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+ZWJ1ZzogZGFydGRldmMK""",
   "test/app_test.dart",
   "text",
   """QFRhZ3MoY29uc3QgWydhb3QnXSkKQFRlc3RPbignYnJvd3NlcicpCmltcG9ydCAnZGFydDphc3lu

lib/generators/web_simple_data.dart

@@ -63,7 +63,8 @@ b20KI2F1dGhvcjogX19hdXRob3JfXyA8ZW1haWxAZXhhbXBsZS5jb20+CgplbnZpcm9ubWVudDoK
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-aXRlcgo=""",
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+ZXZjLgojd2ViOgojICBjb21waWxlcjoKIyAgICBkZWJ1ZzogZGFydGRldmMK""",
   "web/index.html",
   "text",
   """PCFET0NUWVBFIGh0bWw+Cgo8IS0tCiAgQ29weXJpZ2h0IChjKSBfX3llYXJfXywgX19hdXRob3Jf

templates/web-angular/pubspec.yaml

@@ -25,3 +25,8 @@ transformers:
 - test/pub_serve:
     $include: test/**_test.dart
 - dart_to_js_script_rewriter
+
+# Enable these settings to have pub serve use dartdevc.
+#web:
+#  compiler:
+#    debug: dartdevc

templates/web-simple/pubspec.yaml

@@ -16,3 +16,8 @@ dev_dependencies:
 
 transformers:
 - dart_to_js_script_rewriter
+
+# Enable these settings to have pub serve use dartdevc.
+#web:
+#  compiler:
+#    debug: dartdevc