#2: Add compression to channels/ folder

Can use following Python script to compress existing uncompressed
`channels/` folder.

```py

import os, shutil

path = 'channels/'

os.chdir(path)

d = next(os.walk('.'))[1]
for channelIndex, channelId in enumerate(d):
    print(f'{channelIndex} / {len(d)}: {channelId}')
    shutil.make_archive(channelId, 'zip', channelId)
    shutil.rmtree(channelId)
```

main.cpp

@@ -17,8 +17,10 @@ void createDirectory(string path),
      print(ostringstream* toPrint),
      treatComment(unsigned short threadId, json comment, string channelId),
      treatChannelOrVideo(unsigned short threadId, bool isChannel, string id, string channelToTreat),
-     treatChannels(unsigned short threadId);
-string getHttps(string url);
+     treatChannels(unsigned short threadId),
+     deleteDirectory(string path);
+string getHttps(string url),
+       exec(string cmd);
 size_t writeCallback(void* contents, size_t size, size_t nmemb, void* userp);
 bool doesFileExist(string filePath),
      writeFile(unsigned short threadId, string filePath, string option, string toWrite);
@@ -100,6 +102,10 @@ void treatChannels(unsigned short threadId)
 
         treatChannelOrVideo(threadId, true, channelToTreat, channelToTreat);
 
+        // As I haven't found any well-known library that compress easily a directory, I have chosen to rely on `zip` cli.
+        exec("cd " + channelToTreatDirectory + " && zip -r ../" + channelToTreat + ".zip *");
+        deleteDirectory(channelToTreatDirectory);
+
         PRINT(threadId, commentsCount << " comments were found for this channel.")
         commentsCount = 0;
         requestsPerChannel = 0;
@@ -229,6 +235,22 @@ void treatComment(unsigned short threadId, json comment, string channelId)
     commentsCount++;
 }
 
+string exec(string cmd)
+{
+    array<char, 128> buffer;
+    string result;
+    unique_ptr<FILE, decltype(&pclose)> pipe(popen(cmd.c_str(), "r"), pclose);
+    if (!pipe)
+    {
+        throw runtime_error("popen() failed!");
+    }
+    while (fgets(buffer.data(), buffer.size(), pipe.get()) != nullptr)
+    {
+        result += buffer.data();
+    }
+    return result;
+}
+
 bool writeFile(unsigned short threadId, string filePath, string option, string toWrite)
 {
     FILE* file = fopen(filePath.c_str(), option.c_str());
@@ -256,6 +278,11 @@ void createDirectory(string path)
     mkdir(path.c_str(), S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
 }
 
+void deleteDirectory(string path)
+{
+    filesystem::remove_all(path);
+}
+
 string getDate()
 {
     auto t = time(nullptr);