check-strings.sh should check all generated sources, not only lit-magic-strings.inc.h

[ossy-szeged]

CI runs check-strings.sh to check if jerry-core/lit/lit-magic-strings.inc.h is up-to-date, but it doesn't check other generated sources. We could extend it to check them too.

gen-strings.py generates these sources:

• jerry-core/ecma/base/ecma-error-messages.inc.h
• jerry-core/lit/lit-magic-strings.inc.h
• jerry-core/parser/js/parser-error-messages.inc.h

Maybe check-strings.sh can be extended to check all of them or check-strings.sh can be integrated to gen-strings.py