Add TS lint testing and @typescript-eslint/explicit-module-boundary-types warning (#24)

We want to use @typescript-eslint/explicit-module-boundary-types and will have it as a warning for now to not disrupt us as much. Later on we will make it an error.
This is the first TS rule we are adding in this configuration, therefore, the ts eslint config and a ts file for testing local eslint issues are now part of testing.

Author: FSVetaz

demo/example.ts

@@ -0,0 +1,9 @@
+export function someFunc({ prop1 }) {
+  console.log({ prop1 })
+}
+
+export function someFunc2(prop1): void {}
+
+const unusedVar = 3
+
+type UnusedType = number

demo/test/linting-config.test.js

@@ -25,3 +25,7 @@ test('Should apply our custom linting rules consistently', async (t) => {
 test('Should apply a consistent overall eslint configuration', async (t) => {
   return processFile(t, 'local-linting-final-config.json') // If this fails, go cry to mommy
 })
+
+test('Should apply a consistent overall eslint configuration for TS', async (t) => {
+  return processFile(t, 'local-linting-final-config-ts.json') // If this fails, go cry to mommy
+})

demo/test/snapshots/format-config.js

@@ -5,25 +5,38 @@
 /* eslint no-console: "off" -- node scripts use the console, so disable for the whole file */
 
 const FS = require('fs')
-const finalConfig = require('./local-linting-final-config.json')
+const finalJsConfig = require('./local-linting-final-config.json')
+const finalTsConfig = require('./local-linting-final-config-ts.json')
 
-const formattedRules = Object.fromEntries(
-  Object.entries(finalConfig?.rules ?? {}).sort(([ruleNameA], [ruleNameB]) => {
-    if (ruleNameA > ruleNameB) return 1
-    if (ruleNameB > ruleNameA) return -1
-    return 0
-  })
+const parseConfig = (config) => {
+  return {
+    ...config,
+    rules: Object.fromEntries(
+      Object.entries(config?.rules ?? {}).sort(([ruleNameA], [ruleNameB]) => {
+        if (ruleNameA > ruleNameB) return 1
+        if (ruleNameB > ruleNameA) return -1
+        return 0
+      })
+    ),
+    parser: config?.parser?.split('node_modules')[1],
+  }
+}
+
+const finalJsConfigName = 'local-linting-final-config'
+FS.writeFile(
+  `./demo/test/snapshots/${finalJsConfigName}.json`,
+  JSON.stringify(parseConfig(finalJsConfig), null, 2),
+  (err) => {
+    if (err) console.log(`There was an error writing to ${finalJsConfigName}.json file:`, err)
+  }
 )
 
+const finalTsConfigName = 'local-linting-final-config-ts'
 FS.writeFile(
-  './demo/test/snapshots/local-linting-final-config.json',
-  JSON.stringify(
-    { ...finalConfig, rules: formattedRules, parser: finalConfig.parser?.split('eslint-config-tree')[1] },
-    null,
-    2
-  ),
+  `./demo/test/snapshots/${finalTsConfigName}.json`,
+  JSON.stringify(parseConfig(finalTsConfig), null, 2),
   (err) => {
-    if (err) console.log('There was an error writing to local-linting-final-config.json file:', err)
+    if (err) console.log(`There was an error writing to ${finalTsConfigName}.json file:`, err)
   }
 )