docs: fix-vtap-cert: detailed patch usages

Signed-off-by: Cuynu <cuynu@proton.me>

docs/fix-vtap-cert.md

@@ -0,0 +1,56 @@
+# Fix VTAP Certificate usage
+
+This patch can't be applied just by cloning regular repo and apply, I already mentioned it requires specific `firmware` (and `profile` for older base) in `fixcert` folder to function
+
+It can also revert new detection behavior of V-Key (VTAP) like SELinux check, LSPosed, Zygisk check, etc (choose v6.4.78 blobs or older, max to v6.4.53)
+
+```
+# from fix_vtap_cert.sh : 
+
+# What is [firmware] and [profile]?
+# It contains the firmware and certificate for VTAP to communicate with the app connection
+# Both [firmware] and [profile] is encrypted with base64 format.
+# We do not provide it in the project source, but you can get it from the app itself, in [assets] folder.
+```
+
+## How to apply it?
+
+- You can take `firmware` and `profile` file from older app base, then copy to `fixcert` folder in `MBCPApp/` or clone the following repo (it has blobs for some versions) 
+
+```
+# clone vkey vtap blobs repo
+git clone https://git.disroot.org/cuynu/vtapfw_blobs.git
+cd vtapfw_blobs
+
+# in vtapfw_blobs folder, the structure are like this
+[cuynu@x99e vtapfw_blobs] $ tree
+.
+├── README.md
+├── v6.4.66
+│   ├── firmware
+│   └── profile
+├── v6.4.75
+│   ├── firmware
+│   └── profile
+└── v6.5.2
+    ├── firmware
+    └── profile
+```
+
+- Just choose the proper blobs you want to use, then copy it to `fixcert` folder in `MBCPApp` (in this example i'll use v6.4.75 one, `mbbpatch` cloned in home folder)
+```
+cp v6.4.75/firmware ~/mbbpatch/MBCPApp/fixcert
+# DO NOT copy profile if you are patching newer base then the blobs one, otherwise it will fail certificate check.
+cp v6.4.75/profile ~/mbbpatch/MBCPApp/fixcert
+```
+
+Then run patcher again `./mbcpapp.sh` -> `Patch App` -> `Fix VTAP Certificate` -> it will work :)
+
+After installed the patched app, if you have previous data, the old one may still present there, at this point delete with
+```
+su -c rm -f /data/data/com.mbmobile/firmware
+su -c rm -f /data/data/com.mbmobile/profile
+```
+
+
+