chore: add ESLint linting to build pipeline (#4)

Add TypeScript ESLint with recommended rules and integrate
the lint step into the CI workflow.

Author: gmegidish

.github/workflows/build.yml

@@ -36,6 +36,9 @@ jobs:
     - name: Audit
       run: npm audit --audit-level high --omit dev
 
+    - name: Lint
+      run: npm run lint
+
     - name: Update version
       if: github.ref_type == 'tag'
       env:

eslint.config.mjs

@@ -0,0 +1,21 @@
+import tseslint from "@typescript-eslint/eslint-plugin";
+import tsparser from "@typescript-eslint/parser";
+
+export default [
+  {
+    files: ["src/**/*.ts"],
+    languageOptions: {
+      parser: tsparser,
+      parserOptions: {
+        ecmaVersion: 2020,
+        sourceType: "module",
+      },
+    },
+    plugins: {
+      "@typescript-eslint": tseslint,
+    },
+    rules: {
+      ...tseslint.configs.recommended.rules,
+    },
+  },
+];