Refactor code to comply with ESLint rules

Major refactoring using ESLint with rules from AirBnb and Vue.

Enable most of the ESLint rules and do necessary linting in the code.
Also add more information for rules that are disabled to describe what
they are and why they are disabled.

Allow logging (`console.log`) in test files, and in development mode
(e.g. when working with `npm run serve`), but disable it when
environment is production (as pre-configured by Vue). Also add flag
(`--mode production`) in `lint:eslint` command so production linting is
executed earlier in lifecycle.

Disable rules that requires a separate work. Such as ESLint rules that
are broken in TypeScript: no-useless-constructor (eslint/eslint#14118)
and no-shadow (eslint/eslint#13014).

src/domain/Category.ts

@@ -3,40 +3,46 @@ import { IScript } from './IScript';
 import { ICategory } from './ICategory';
 
 export class Category extends BaseEntity<number> implements ICategory {
-    private allSubScripts: ReadonlyArray<IScript> = undefined;
+  private allSubScripts: ReadonlyArray<IScript> = undefined;
 
-    constructor(
-        id: number,
-        public readonly name: string,
-        public readonly documentationUrls: ReadonlyArray<string>,
-        public readonly subCategories?: ReadonlyArray<ICategory>,
-        public readonly scripts?: ReadonlyArray<IScript>) {
-        super(id);
-        validateCategory(this);
-    }
+  constructor(
+    id: number,
+    public readonly name: string,
+    public readonly documentationUrls: ReadonlyArray<string>,
+    public readonly subCategories?: ReadonlyArray<ICategory>,
+    public readonly scripts?: ReadonlyArray<IScript>,
+  ) {
+    super(id);
+    validateCategory(this);
+  }
 
-    public includes(script: IScript): boolean {
-        return this.getAllScriptsRecursively().some((childScript) => childScript.id === script.id);
-    }
+  public includes(script: IScript): boolean {
+    return this.getAllScriptsRecursively().some((childScript) => childScript.id === script.id);
+  }
 
-    public getAllScriptsRecursively(): readonly IScript[] {
-        return this.allSubScripts || (this.allSubScripts = parseScriptsRecursively(this));
+  public getAllScriptsRecursively(): readonly IScript[] {
+    if (!this.allSubScripts) {
+      this.allSubScripts = parseScriptsRecursively(this);
     }
+    return this.allSubScripts;
+  }
 }
 
 function parseScriptsRecursively(category: ICategory): ReadonlyArray<IScript> {
-    return [
-        ...category.scripts,
-        ...category.subCategories.flatMap((c) => c.getAllScriptsRecursively()),
-    ];
+  return [
+    ...category.scripts,
+    ...category.subCategories.flatMap((c) => c.getAllScriptsRecursively()),
+  ];
 }
 
 function validateCategory(category: ICategory) {
-    if (!category.name) {
-        throw new Error('undefined or empty name');
-    }
-    if ((!category.subCategories || category.subCategories.length === 0) &&
-        (!category.scripts || category.scripts.length === 0)) {
-        throw new Error('A category must have at least one sub-category or script');
-    }
+  if (!category.name) {
+    throw new Error('undefined or empty name');
+  }
+  if (
+    (!category.subCategories || category.subCategories.length === 0)
+      && (!category.scripts || category.scripts.length === 0)
+  ) {
+    throw new Error('A category must have at least one sub-category or script');
+  }
 }