Sonarqube support with ESLint

[4n4n4s]

Added sonarqube analysis.

To enable you:

1. need to create an organization on sonarcloud with your github user and setup a project for free-games-claimer github project
2. create a token at https://sonarcloud.io/account/security and add it as "SONAR_TOKEN" to the projects secrets
3. https://sonarcloud.io/project/analysis_method?id=vogler_free-games-claimer change analysis to not use "Automatic Analysis"

In the .eslintrc.cjs we can also add new rules like I added for now 'semi': 'error' so we enforce to have semicolons at the end of each line.

You can also use the ESLint addon in VSCode/Coduim and it also uses the .eslintrc.cjs

We can later also add test coverage and status icons to the README.md about project status.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[vogler]

Thanks!
Signing up and adding the repo on sonarcloud was enough for its automatic analysis. However, this has the following limitations:

• Branch analysis (analysis of non-pull request branches other than the main branch) is not supported.
• Code coverage information is not supported.
• Import of external rule engine reports is not supported.

This PR adds a GitHub Action for sonarcloud as shown here: https://github.com/SonarSource/sonarcloud-github-action

This allows to integrate eslint into the sonarcloud results: https://docs.sonarsource.com/sonarcloud/enriching/external-analyzer-reports/#javascript

.eslintrc.cjs is close to what npm init @eslint/config would generate, but extends a minimal eslint:recommended instead of something like https://github.com/airbnb/javascript which would cause lots of warnings.

Tried the airbnb style guide for epic-games.js but ended up disabling a lot of rules:

/* eslint-disable no-restricted-syntax */
/* eslint-disable arrow-parens */
/* eslint-disable no-mixed-operators */
/* eslint-disable eqeqeq */
/* eslint-disable no-await-in-loop */
/* eslint-disable no-console */
/* eslint-disable max-len */

So, extending eslint:recommended seems like the better idea.
Only thing I had to adjust was 'no-unused-vars': ["error", { "argsIgnorePattern": "^_" }] to not have it warn about _ as unused arg. - https://eslint.org/docs/latest/rules/no-unused-vars#argsignorepattern
Also, no-undef needs to be disabled for JS evaluated in the browser context for it to not complain about undef. window etc.

[vogler]

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