[FEATURE] TWRP Add a tutorial to flash TWRP

[MartinX3]

Is your feature request related to a problem? Please describe.
Add a tutorial to flash TWRP

Describe the solution you'd like
Like https://sx.ix5.org/info/flashing-aosp-on-xperia-xz/

Describe alternatives you've considered
My XDA thread instructions

Additional context
N/A