feat(js): add solution and documentation for easy challenge 9 - Word frequency counter

Author: IbatoLionDev

1-EASY/JavaScript/9-word-frequency-counter/article.md

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+# Challenge Description and Solution
+
+## English Version
+
+### Challenge Description
+Create a function that counts the frequency of each word in a given text. Consider normalization of case and removal of punctuation.
+
+### Code Explanation
+The `wordFrequency` function converts the text to lowercase, removes punctuation using a regex, and then counts the frequency of each word using an object.
+
+### Relevant Code Snippet
+
+```javascript
+function wordFrequency(text) {
+    const punctuationRegex = /[!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~]/g;
+    text = text.toLowerCase().replace(punctuationRegex, '');
+    const words = text.split(/\s+/);
+    const freq = {};
+    for (const word of words) {
+        if (word.length === 0) continue;
+        freq[word] = (freq[word] || 0) + 1;
+    }
+    return freq;
+}
+```
+
+### Example Usage
+
+```javascript
+const sampleText = "Hello world! Hello everyone. Welcome to the world of Python.";
+const frequencies = wordFrequency(sampleText);
+for (const [word, count] of Object.entries(frequencies)) {
+    console.log(`'${word}': ${count}`);
+}
+```
+
+---
+
+## Versión en Español
+
+### Descripción del Reto
+Crea una función que cuente la frecuencia de cada palabra en un texto dado. Considera la normalización de mayúsculas y minúsculas y la eliminación de signos de puntuación.
+
+### Explicación del Código
+La función `wordFrequency` convierte el texto a minúsculas, elimina signos de puntuación usando una expresión regular, y luego cuenta la frecuencia de cada palabra utilizando un objeto.
+
+### Fragmento de Código Relevante
+
+```javascript
+function wordFrequency(text) {
+    const punctuationRegex = /[!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~]/g;
+    text = text.toLowerCase().replace(punctuationRegex, '');
+    const words = text.split(/\s+/);
+    const freq = {};
+    for (const word of words) {
+        if (word.length === 0) continue;
+        freq[word] = (freq[word] || 0) + 1;
+    }
+    return freq;
+}
+```
+
+### Ejemplo de Uso
+
+```javascript
+const sampleText = "Hello world! Hello everyone. Welcome to the world of Python.";
+const frequencies = wordFrequency(sampleText);
+for (const [word, count] of Object.entries(frequencies)) {
+    console.log(`'${word}': ${count}`);
+}

1-EASY/JavaScript/9-word-frequency-counter/proposed-solution/main.js

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+// Challenge: Create a function that counts the frequency of each word in a given text.
+// Consider normalization of case and removal of punctuation.
+
+function wordFrequency(text) {
+    const punctuationRegex = /[!"#$%&'()*+,\-./:;<=>?@[\\\]^_`{|}~]/g;
+    text = text.toLowerCase().replace(punctuationRegex, '');
+    const words = text.split(/\s+/);
+    const freq = {};
+    for (const word of words) {
+        if (word.length === 0) continue;
+        freq[word] = (freq[word] || 0) + 1;
+    }
+    return freq;
+}
+
+// Example usage
+const sampleText = "Hello world! Hello everyone. Welcome to the world of Python.";
+const frequencies = wordFrequency(sampleText);
+for (const [word, count] of Object.entries(frequencies)) {
+    console.log(`'${word}': ${count}`);
+}