message: document patchparams extras
diff: * `Api::watch` returns `Result<WatchEvent>` rather than `WatchEvent`
  * `WatchEvent::Bookmark` added to enum
  * `ListParams::allow_bookmarks` added
  + * `PatchParams::default_apply` ctor added
  + * `PatchParams` builder mutators: `::force` and `::dry_run` added
  0.31.0 / 2020-03-27
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