[README.md] add --sort flag
@@ -84,6 +84,7 @@ Specify where to add the crate:
for `dev-dependencies` or `build-dependencies`.
Options:
+ --sort Keep dependencies sorted
--upgrade=<method> Choose method of semantic version upgrade. Must be one of
"none" (exact version), "patch" (`~` modifier), "minor"
(`^` modifier, default), or "all" (`>=`).
