KiCad : Ignore lock files for KiCad v7

[IamPhytan]

Reasons for making this change:

KiCad v7 now creates lock files when opening a PCB schematic or layout. These lock files should be ignored in version control, as their presence in a repository can lead to errors when opening a project.

Links to documentation supporting these rule changes:

There are a few discussions on the KiCad forum that supports ignoring *.lck lock files. Here is an example.

[SubaruArai]

Another example of the lock file causing trouble: https://forum.kicad.info/t/opening-schematic-error/43525

[atoomnetmarc]

Works for me.