feat: Add app.getLocaleCountryCode() method for region detection (#15035)

* Add method to get system´s user region

* Fix linter

* Remove auto types

* Improved detection for POSIX

* Change name, add specs, minor fixes

* Remove left overs

* Fix locale test

* Fix Linux test

* Coding style fixes

* Fix docs

* Add test excaption for Linux

* fix spelling

* Polishing

spec/api-app-spec.js

@@ -122,6 +122,17 @@ describe('app module', () => {
     })
   })
 
+  describe('app.getLocaleCountryCode()', () => {
+    it('should be empty or have length of two', () => {
+      let expectedLength = 2
+      if (isCI && process.platform === 'linux') {
+        // Linux CI machines have no locale.
+        expectedLength = 0
+      }
+      expect(app.getLocaleCountryCode()).to.be.a('string').and.have.lengthOf(expectedLength)
+    })
+  })
+
   describe('app.isPackaged', () => {
     it('should be false durings tests', () => {
       expect(app.isPackaged).to.be.false()