Add a troubleshooting guide on the blinking in git bash

[zadjii-msft]

Folks complain way too often about this. See microsoft/terminal#10005, microsoft/terminal#7688 et al.

Massage this into a actual paragraph:

This is actually by design. The Terminal is finally just obeying what git bash is telling it to do. For more info, see:

dup microsoft/terminal#9430
dup microsoft/terminal#9111
dup microsoft/terminal#7200

To fix: nano ~/.inputrc and add the text set bell-style none or set bell-style audible. Press Ctrl + O and Ctrl + X to Save and Exit.
I found this behaviour to be really distracting/disurbing.
The regular Git Bash terminal does exhibit this behaviour, though I can confirm that /c/Program Files/Git/etc/.inputrc does contain set bell-style visible (and that command is not overwritten by anything in .inputrc.

[mattwojo]

Added. :) Thanks @zadjii-msft !
#356