Add command chmod 777 in README (issue #10)

This is required when the host user has a different UID from the user in the
container (UID 1001).

README.md

@@ -55,13 +55,15 @@ Run with custom home directories on host to persist data (WeeChat ≥ 3.2, using
 
 ```bash
 mkdir -p ~/.weechat-container/config ~/.weechat-container/data ~/.weechat-container/cache
+chmod 777 ~/.weechat-container/config ~/.weechat-container/data ~/.weechat-container/cache
 docker run -it -v $HOME/.weechat-container/config:/home/user/.config/weechat -v $HOME/.weechat-container/data:/home/user/.local/share/weechat -v $HOME/.weechat-container/cache:/home/user/.cache/weechat weechat/weechat
 ```
 
 Run with a custom single home directory on host to persist data (any WeeChat version):
 
 ```bash
 mkdir -p ~/.weechat-container
+chmod 777 ~/.weechat-container
 docker run -it -v $HOME/.weechat-container:/home/user/.weechat weechat/weechat weechat -d /home/user/.weechat
 ```