feat: rewrite programming-challenges CLI (#3)

challenges/first-non-repeating-character/solutions/javascript/function/README.md

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+# first-non-repeating-character/javascript/function
+
+Created by [@Divlo](https://github.com/Divlo) on 6 June 2021.

challenges/first-non-repeating-character/solutions/javascript/function/package.json

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+{
+  "type": "module"
+}

challenges/first-non-repeating-character/solutions/javascript/function/solution.js

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+import readline from 'readline'
+
+const input = []
+const readlineInterface = readline.createInterface({
+  input: process.stdin,
+  output: process.stdout
+})
+readlineInterface.on('line', (value) => {
+  input.push(value)
+})
+readlineInterface.on('close', solution)
+
+const firstNonRepeatingCharacter = (string) => {
+  const lettersCount = {}
+  for (let index = 0; index < string.length; index++) {
+    const character = string[index]
+    if (lettersCount[character] == null) {
+      lettersCount[character] = {
+        total: 1,
+        firstIndex: index,
+        value: character
+      }
+    } else {
+      lettersCount[character].total += 1
+    }
+  }
+  let result = null
+  for (const character in lettersCount) {
+    const characterObject = lettersCount[character]
+    if (characterObject.total === 1) {
+      if (result == null) {
+        result = characterObject
+      } else if (characterObject.firstIndex < result.firstIndex) {
+        result = characterObject
+      }
+    }
+  }
+  if (result == null) {
+    return ''
+  }
+  return result.value
+}
+
+function solution() {
+  console.log(firstNonRepeatingCharacter(input[0]))
+}