Test Fluent.js for complex accessibility strings

[jessegreenberg]

After #990, we are going to try Fluent.js to support i18n for complex accessibility strings.

In this issue Ill track changes and progress. First, we are going to bring Fluent in as a dependency. Then, we are going to try it out with 3 sims. We are then going to test the strings with translators to get feedback.

[jessegreenberg]

The latest version of Fluent.js was not compatible with our preload system/sherpa which requires a standalone built file. We found a build in this format at https://www.npmjs.com/package/fluent. It is 5 years old.

We will want to figure out how we can get the latest version. For other POSE reasons, PhET is exploring how we can use a more standard way of importing dependencies. But if that isn't figured out, we will need to find a way to bundle a more recent version of Fluent so it can be used in sherpa.

[jessegreenberg]

The above commits complete a first pass at using Fluent in ohms-law for accessibility strings.