Add _javascript_1 file icon to seti icon theme for test.mjs

[desean1625]

Can we add test.mjs extension to seti icon theme?

This file extension is the default for node js test runner.

It would be nice to have the same theming as the regular javascript for javascript modules.

microsoft/vscode#210245

[gian1200]

Not only test.mjs, but add .mjs to all rules that have .js

seti-ui/styles/components/icons/mapping.less

Line 200 in 8fef6fa

.icon-set(".js", "javascript", @yellow);

Also special cases such as .spec.mjs, .test.mjs, stylelint.config.mjs, .eslintrc.mjs, new eslint.config.mjs flat config file, karma.conf.cjs, karma.conf.mjs, webpack.{config,dev,prod,common}.mjs, etc.

Update:
there is already a PR for

• Webpack: Webpack icon: support .mjs file extension #700
• ESLint Flat Config: feat: add icon for eslint flat config file #691