feat(tools): introduce knip to find unused files, dependencies & exports (freeCodeCamp#47836)

* chore(deps): add exportman to devDependencies

* chore(client): add exportman config for /client folder

* chore: migrate from exportman to knip

* chore: add npm script

* chore: prepare npm script for usage in CI

Author: webpro

config/knip/knip.dev.json

@@ -0,0 +1,27 @@
+{
+  "client":{
+    "dev": true,
+    "exclude": ["dependencies"],
+    "entryFiles": [
+      "gatsby-*.js",
+      "src/pages/*.tsx",
+      "src/templates/Challenges/**/{s,S}how.tsx",
+      "src/templates/Introduction/**/{intro,super-block-intro}.tsx",
+      "src/**/*.test.{js,ts,tsx}"
+    ],
+    "projectFiles": [
+      "src/**/*.{js,ts,tsx}",
+      "!static/misc/*.js",
+      "!i18n/schema-validation.ts",
+      "!plugins/**",
+      "!postcss.config.js",
+      "!src/client/frame-runner.ts",
+      "!src/client/workers/**",
+      "!webpack-workers.js",
+      "!**/i18n/config-for-tests.ts",
+      "!**/__mocks__/**",
+      "!**/__fixtures/**",
+      "!**/node_modules/**"
+    ]
+  }
+}

config/knip/knip.json

@@ -0,0 +1,28 @@
+{
+  "client":{
+    "exclude": ["dependencies"],
+    "entryFiles": [
+      "gatsby-*.js",
+      "src/html.tsx",
+      "src/pages/*.tsx",
+      "src/templates/Challenges/**/{s,S}how.tsx",
+      "src/templates/Introduction/**/{intro,super-block-intro}.tsx"
+    ],
+    "projectFiles": [
+      "**/*.{js,ts,tsx}",
+      "!static/misc/*.js",
+      "!i18n/schema-validation.ts",
+      "!plugins/**",
+      "!postcss.config.js",
+      "!src/client/frame-runner.ts",
+      "!src/client/workers/**",
+      "!webpack-workers.js",
+      "!**/*.test.{js,ts,tsx}",
+      "!**/i18n/config-for-tests.ts",
+      "!**/__mocks__/**",
+      "!**/__fixtures/**",
+      "!**/node_modules/**",
+      "!**/*.d.ts"
+    ]
+  }
+}