Completed the todo - Divided the constants.js of redux into submodules

[Vishawdeep-Singh]

Completed TODO at the top of constants.js

Changes: I created a folder called “constants” and sub-modules of Redux constants, such as “fileActions.js”, “errorActions.js”, and so on. I then imported these sub-modules into the original “constants.js” file, spread them, and exported them.

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[raclim]

Thanks so much for taking the time to work on this!

After giving it some thought, unfortunately I don't think we'll be able to go with this since we're hoping to migrate to using Redux Toolkit, which I believe eliminates the need for the constants.js folder. I'm sorry that we couldn't get this in, but if you'd like please feel free to jump in and continue the Redux Toolkit migration work that some folks have started!