build: Replace Codelyzer and TSLint with Angular ESLint

Migrate from the deprecated TSLint to Angluar ESLint. Also fix current
linting issues in the code, in particular:

- Use strict equals operators (=== and !==)
- Remove empty lifecycle methods (mostly ngOnInit)
- Output bindings including aliases should not be named as standard dom
  events (submit)
- Async pipe results should not be negated

src/app/shared/language-selector/language-selector.component.ts

@@ -1,5 +1,5 @@
 /** Angular Imports */
-import { Component, OnInit } from '@angular/core';
+import { Component } from '@angular/core';
 import { UntypedFormControl } from '@angular/forms';
 
 /** Custom Services */
@@ -17,7 +17,7 @@ import { SettingsService } from 'app/settings/settings.service';
   templateUrl: './language-selector.component.html',
   styleUrls: ['./language-selector.component.scss']
 })
-export class LanguageSelectorComponent implements OnInit {
+export class LanguageSelectorComponent {
 
   /** Language selector form control. */
   languageSelector = new UntypedFormControl();
@@ -31,9 +31,6 @@ export class LanguageSelectorComponent implements OnInit {
     this.languageSelector.setValue(this.currentLanguage);
   }
 
-  ngOnInit() {
-  }
-
   /**
    * Sets a new language to be used by the application.
    * @param {string} language New language.