docs: fix typo (protobufjs#1241)

Author: Jason-Cooke

README.md

@@ -653,9 +653,9 @@ Translates between file formats and generates static code.
   --no-beautify    Does not beautify generated code.
   --no-comments    Does not output any JSDoc comments.
 
-  --force-long     Enfores the use of 'Long' for s-/u-/int64 and s-/fixed64 fields.
-  --force-number   Enfores the use of 'number' for s-/u-/int64 and s-/fixed64 fields.
-  --force-message  Enfores the use of message instances instead of plain objects.
+  --force-long     Enforces the use of 'Long' for s-/u-/int64 and s-/fixed64 fields.
+  --force-number   Enforces the use of 'number' for s-/u-/int64 and s-/fixed64 fields.
+  --force-message  Enforces the use of message instances instead of plain objects.
 
 usage: pbjs [options] file1.proto file2.json ...  (or pipe)  other | pbjs [options] -
 ```