tests: Add test cases for unexpected delimiter

Add some simple tests for encountering unexpected delimiters.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Consistent result types/names

One function had named return values, keep is consistent with other
functions.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Add Go Doc comments

Add Go Doc comments to exported names.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Add encode/decode commands

Add CLI tools to encode or decode from stdin to stdout.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

Setup Go Module

* Create go.mod file
* Add Github Go workflow Action to build and test module