Updated Installation Instruction to be compatible with latest NvChad release 2.5

[yashasolutions]

NvChad release 2.5 do not support custom folder anymore (as well as a few other minor changes, all described in their Release announcement)

Since they provide a migration script which works well out of the box, I have updated the installation instruction with the extra steps required to run the migration script.

Also, NvChad base repo for installation has changed, as documented in the install docs, so I have update this as well.

It should work fine and save someone else 1h of digging around.