Set schemas path relative to executable

[per1234]

Previously, the schemas path was defined relative to the working directory, but the schemas will be stored in a path
relative to the arduino-check executable, which may not necessarily be in the working directory.

Unfortunately, this breaks the ability to run the code using go run because the executable path is the temporary directory the program is run from and the schemas are not under that path. I did some searching for a solution to this and found none worth consideration (example: https://github.com/golang/go/issues/5157, https://stackoverflow.com/questions/18537257/how-to-get-the-directory-of-the-currently-running-file).

I would welcome any suggestions for how to properly handle defining the path to data files that accompany the tool.

[silvanocerza]

If you still want the ability to run it using go run probably the best best would be to pass the schema path as an argument to the tool.

[per1234]

I don't foresee the users of the tool ever having the need to specify a custom schemas path, so adding this setting would be only for the sake of go run compatibility. I am just using go build && ./arduino-check so it doesn't bother me to do without go run.

My concern is about whether this will be a problem for other contributors. I suppose it's best to wait to see whether there are any complaints before adding special provisions for this usage.