add gitattributes to reduce composer package size

[Sysix]

adding all files to .gitattributes, which the composer package don't need.

Should always include:

• Pipline/Github Actions
• Tests Files
• Docs
• etc.

[duncanmcclean]

Thanks! I always wondered what that file was for, now I know.

[Sysix]

you can do much more with it, but for the beginning it is enough :)