feat(testing): add jest as unit test framework (#3517)

[spectrum-branch]

Description of the Change

• Adds jest unit test framework to Firebot. An example unit test is staged there to allow running of tests with this foundation. This example test can be removed as "real" tests are added.
• In order to keep the linter and typescript happy, I had to create a second eslint configuration block for the test files and a separate file for the tsconfig. The production config should remain the same despite any refactoring. The reason for creating a second configuration for tests stems from rootDir in tsconfig.json being set to './src', as this does not cover the typical directory of the ./tests folder, so npm CLI commands would complain. In no way did I want to potentially affect how production builds function, so I did not dare change rootDir. If the devs decide to change this value, it could lead to a bit of unification of this configuration. I researched both vitest and jest for this situation as a bit of due diligence, and they both would be affected by this.
• The jest configuration was generated using npm init jest, in order to create the resultant jest.config.ts file. This configuration can be changed as needed, and even be regenerated by running the same npm init jest command again and giving different answers. The below includes the whole question/answer dialogue with the generator:

❯ npm init jest
Need to install the following packages:
create-jest@30.4.2
Ok to proceed? (y) y

npm warn deprecated inflight@1.0.6: This module is not supported, and leaks memory. Do not use it. Check out lru-cache if you want a good and tested way to coalesce async requests by a key value, which is much more comprehensive and powerful.
npm warn deprecated glob@7.2.3: Old versions of glob are not supported, and contain widely publicized security vulnerabilities, which have been fixed in the current version. Please update. Support for old versions may be purchased (at exorbitant rates) by contacting i@izs.me
npm warn deprecated glob@10.5.0: Old versions of glob are not supported, and contain widely publicized security vulnerabilities, which have been fixed in the current version. Please update. Support for old versions may be purchased (at exorbitant rates) by contacting i@izs.me

> firebotv5@5.66.5 npx
> create-jest


The following questions will help Jest to create a suitable configuration for your project

✔ Would you like to use Typescript for the configuration file? … yes
✔ Choose the test environment that will be used for testing › node
✔ Do you want Jest to add coverage reports? … no
✔ Which provider should be used to instrument code for coverage? › v8
✔ Automatically clear mock calls, instances, contexts and results before every test? … yes

I left behind the comments that were generated in the jest.config.ts file which detail the various options, but they could just as easily be removed. This is a good moment to discuss any changes to this configuration based on the preferences of the devs.

Applicable Issues

#3517

Testing

• Typical smoke tests should cover this, in addition to the new command npm run test which should run all tests. The application is intended to run normally/exactly the same as before.
• I tested by ensuring all npm run ... scripts worked, including lint, setup, build, and start.

~/git/Firebot add-unit-testing* ≡
❯ npm run lint

> firebotv5@5.66.6 lint
> grunt lint

Running "shell:eslint" (shell) task

Done.

~/git/Firebot add-unit-testing* ≡ 6s
❯ npm run test

> firebotv5@5.66.6 test
> jest

 PASS  tests/example.spec.ts
  Math tests
    ✓ should add two numbers (1 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.122 s, estimated 1 s
Ran all test suites.

Screenshots