core: Add clang-tidy (#8664)

This adds a .clang-tidy file for us.

It's not a strict requirement to be compliant, but I tuned it to be alright.

src/debug/CrashReporter.hpp

@@ -2,6 +2,6 @@
 
 #include "../defines.hpp"
 
-namespace CrashReporter {
+namespace NCrashReporter {
     void createAndSaveCrash(int sig);
 };