✨ FEATURE: Add import keyword

[LucaDillenburg]

Is your feature request related to a problem? Please describe.
I'm always frustrated when I have to write a very large program because all of the code has to be on the same file.

Describe the solution you'd like
Add an import keyword that merges the files into a single source code while processing it so that the code can be written in different files. The imports can be made on any line.
Code example:
main.asm

store 0x01

import utils.asm
#store 0x01
#add 0x02

sub 0x3

utils.asm

store 0x01
add 0x02

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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