The `<ReleaseSelect>` component now uses RTK instead of DDF. Some
additional small changes were necessary due to Typescript - in
particular, we use a Map() to store the releases (in order to ensure
they appear in the correct order) and .tsconfig had to be modified to
allow iteration over the Map() object.
This commit adds the initial setup for using Typescript in our project.
The tsconfig.json is very minimal at this point, we will introduce
stricter rules as our Typescript migration progresses.
