Add guide to UEFI Secure Boot

[some100]

adds a guide to uefi secure boot

includes using shim with opencore

[some100]

also #14 exist but its been a draft for over 4 years so idk

[perez987]

@some100
You have done an excellent work. Very detailed. I have doubts about this to be managed by devs since is a topic outdated for a long time.
Let me post a few comments in case you see them useful. Feel free to do what you want with the texts of my repos.

There is an easier method to enroll efi images into the firmware, in my opinion not only it is much simpler but it also has much less risk of damaging the BIOS (with the classic method, sometimes you can get a bricked BIOS and have to recover it from a backup BIOS). You can read about it on my GitHub:
UEFI Secure Boot and OpenCore: The easy way (no Linux nor Windows needed)

In the part explaining how to insert secure variables into the firmware I miss modern BIOS images from American Megatrends International (AMI), which are present on many Gigabyte and Asus boards today. It's not a big deal but AMI Aptio V images are not the usual ones these days.
I have screenshots of these BIOS here:
UEFI Secure Boot and OpenCore: How to insert signatures in the UEFI firmware

Finally, the merging of OpenCore Vault with UEFI Secure Boot is poorly explained in Dortania's guide. Maybe it's useful to add a comment on how to do it. You can see my proposal here (I proposed this a while ago in the bug tracker but it has never been implemented):
Apple Secure Boot with OpenCore. Vaulting OpenCore. UEFI Secure Boot.
Go to the last block OpenCore Vault + UEFI Secure Boot.

Anyway, I appreciate the work you've done, completed with instructions for Linux working on shim as well.
I hope it will be taken into account.
Not to mention that developers are unpaid people who have other occupations and hobbies and probably find it difficult to find free time for everything.

[some100]

Included comments on Vaulting with Secure Boot. Thanks for the suggestion