Adding isfshax as an advanced/alternative exploit

[jbmagination]

Me and some others were talking about this so I figured it would be worth making a GitHub issue about since I fully expect we're not the only ones thinking about it.

I think isfshax should be added to the guide - but NOT as the main exploit. I have gripes with it that make it difficult for me to fully sell it as the main exploit for what is largely intended to be a noob-friendly guide.

• Autobooting cannot be setup within the minute_minute GUI - it must be done as a configuration file on your SD card. If you don't set it up, you must use your Power and Eject buttons to navigate which option you want - without access to the GamePad - every time you boot up your Wii U. You also cannot use autobooting without your SD card inserted - the minute_minute GUI will appear every time.
• Enables sigpatches, which were on the guide before when Tiramisu was a thing but were removed when the guide started mainly recommending Aroma instead - and I think that's the right choice. With the Homebrew on Menu plugin, sigpatches are basically unnecessary (unless I'm forgetting something important!)
• Potential SLC corruption. It is considered quite safe, but for this reason, people who want to set it up are currently still advised to make a backup of their SEEPROM, OTP, and SLC.
• Hynix MLCs - who need something like this the most - only make up ~2.5% of Wii U's on the Wii U System Database (link is sorted by MLC). For everyone else, I feel that it's largely not worth the hassle.

However, if they do set it up - especially if they have Hynix MLCs, like myself - and don't fuck things up in the process of setting it up, which I nearly did more than once - it serves as very good brick protection. I am one who likes to tinker and break and touch things I really shouldn't be touching, and isfshax with some backups has already saved my ass quite a few times. It also provides a minimal CFW even if you don't choose to setup direct PayloadLoader access into something like Aroma.