Replace octonode with octokit

[liammulh]

In Rosetta 1.0, we were using a library called octonode for interacting with GitHub's API. It's possible that Rosetta 1.0 was written prior to the release of octokit, which is GitHub's official library for interacting with GitHub's API.

We continued using octonode in Rosetta 2.0 because it was easier than switching to something new. (We were already making a lot of changes in the transition from 1.0 to 2.0.)

I don't think this should be a high priority because octonode works (and if it ain't broke don't fix it), but there are a few advantages I see to using octokit instead of octonode:

1. more popular, better support generally
2. better IDE support (octonode has async methods, but Webstorm doesn't recognize them)
3. better response objects (i.e. response objects that have the HTTP response status code, see long term storage of pl/energy-skate-park failed #376 (comment))

[liammulh]

Octonode is now introducing moderate security vulnerabilities. npm audit yields:

# npm audit report

request  *
Severity: moderate
Server-Side Request Forgery in Request - https://github.com/advisories/GHSA-p8p7-x288-28g6
No fix available
node_modules/request
  octonode  *
  Depends on vulnerable versions of request
  node_modules/octonode

2 moderate severity vulnerabilities

Some issues need review, and may require choosing
a different dependency.

[liammulh]

In the above commits, I added a class LongTermStorage to interface with long-term storage, which is GitHub, as of this writing. This class has a get method and a store method. I made it so that Rosetta now uses these methods instead of issuing Axios requests to raw.githubusercontent.com.

We also get string files from GitHub that are in the sim repos. In the above commits, I added a module getStringFile that uses Octokit instead of issuing a request to raw.githubusercontent.com, except in one place: getEnglishStringKeysAndValues. It's kind of a special module in that the other modules that are getting the string file on the master branch, but the getEnglishStringKeysAndValues module needs a specific SHA.

Before we can do more testing, I need to use Octokit for getEnglishStringKeysAndValues. I need to refactor getStringFile to accept a ref as the second parameter, I think.

[liammulh]

Now that we are using Octokit, the data we get back is what's currently on GitHub. (raw.githubusercontent.com caches requests for about five minutes.)

This means we can close #316, and we might be able to reload the page after a user submits a translation in order to fix #386.

[liammulh]

I think we can also close #376 once this fix is deployed.

[liammulh]

Don't forget to close #343 when this fix is deployed.

[liammulh]

Before we can do more testing, I need to use Octokit for getEnglishStringKeysAndValues. I need to refactor getStringFile to accept a ref as the second parameter, I think.

Done in 7a47a60.

[liammulh]

Deployed in 6021626 (2.0.7).

[liammulh]

This is done. Closing.