Add zsh_sessions entry to zsh (#394)

## Details

Some info on the .zsh_sessions file can be found here:
https://apple.stackexchange.com/questions/427561/macos-zsh-sessions-zsh-history-and-setopt-append-history

It only gets generated on MacOS when using the default terminal
and can be disabled in the user zshenv file.

programs/zsh.json

@@ -1,5 +1,10 @@
 {
     "files": [
+        {
+            "help": "Set this in your zshenv:\n\n```bash\nSHELL_SESSIONS_DISABLE=1\n```\n\nShould only exist on macOS when using the default terminal.\n",
+            "movable": true,
+            "path": "$HOME/.zsh_sessions"
+        },
         {
             "help": "Set this in your zshrc:\n\n```bash\nzstyle ':completion:*' cache-path \"$XDG_CACHE_HOME\"/zsh/zcompcache\n```\n\nYou must manually create the _$XDG_CACHE_HOME/zsh_ directory if it doesn't exist yet.\n",
             "movable": true,