parser: add_schema_from_file: return InvalidFilePath instead of io::Error

[wsipak]

Follow-up to: #291

This is another case where the user would get an io::Error without any information about the path.
With this change, the Error provides the information about the path.

From what I see this was the only use of the implicit conversion from io::Error in

xsd-parser/xsd-parser/src/pipeline/parser/error.rs

Lines 15 to 18 in aeb9f32

	pub enum Error<E> {
	/// An IO error occurred.
	#[error("IO Error: {0}")]
	IoError(#[from] IoError),

I think it's worth considering to drop the #[from] for implicit conversion completely, so that the users of this type must explicitly handle io::Error and produce an error with the path info.