Add missing PutMode enum export

[kamilklyta]

Now it is not possible to pass the mode argument to put or putMany due to missing export.

[vaind]

Thanks, must have gotten lost in the process of cleaning up the exported APIs.

[kamilklyta]

You're welcome 😉

[kamilklyta]

@vaind, if you need some help / contributions, simply let me know, maybe I can help you a little bit.

[vaind]

@vaind, if you need some help / contributions, simply let me know, maybe I can help you a little bit.

Any contributions are greatly appreciated, depends on what kind you prefer. Some ideas of what you could do:

• join the discussion about Query streams/observers Query observer changes #195 or Exceptions Request for comments: Unify exception throwing #182 or Async Async/Await/Futures #49 and Feature request: async put/get #131
• implement some features, e.g. like Unsigned annotation #85, Custom types #93
• have a look at the changes in the null-safety branch if you have any ideas/notice any issues: Dart 2.12 support, null-safety #204 - can be done to various extent, no need to try and view all the changes
• or join the just-starting development of the web version of objectbox Web-capable Box API; based on IndexedDB #185
• and of course you can just create issues if you're missing some features from other database plugins or have other ideas for improvement