Add `Filename` and `Line` in preparation to enhance error reporting.
The extra fields should be suited to provide consise error reporting when an error occurs.

Signed-off-by: Gekko Wrld <[email protected]>

The parser doesn't emit its own errors, it relies on 'errd' package to do so.
This makes it easier to format the error messages in a uniform parsable form.

Instead of:
	Mstari 1: Tumeshindwa kuparse HARAMU
Its:
	Kosa la kisintaksia: h.nr:1:4
	Tumeshindwa kuparse '#'

This gives the user the hint where the problem is and what caused the problem.

Parser errors doesn't exit after display.

Signed-off-by: Gekko Wrld <[email protected]>

Previuos implementation counted the rows and columns inconsistently.
This fix will enable counting to be consistent and better.

- Use strings.Builder in `readString` function instead of naive string concatenation
	This reduces memory allocation and deallocation being done by go making the program efficient.

Signed-off-by: Gekko Wrld <[email protected]>

The line in which the error occured in is now displayed along with the error.
This makes it easier to see what went wrong at a glance without opening the file to confirm.
A caret is placed at the start of the error token to help the user know where they can start fixing from.

Signed-off-by: Gekko Wrld <[email protected]>