fix: incorrect go workspace setup without go.work

[nekomeowww]

Currently, this project isn't contributable or workable after cloned, the Go workspace setup for this project is unavailable and wrong, since it only contains the go.work.sum file with incorrectly defined go.mod which points to internal traceloop-sdk and semconv-ai packages.

This is due to the incorrect configured .gitignore with the line

go-openllmetry/.gitignore

Lines 20 to 21 in 5749e84

	# Go workspace file
	go.work

which ignores the go.work file.

While Go workspace isn't necessarily needed for such library, but I still maintained the content of go.work.sum not to change a lot to prevent potential dependencies breaking and mismatching, or even vendor vulnerabilities. If you would like to, or feel uncomfortable with go.work somehow, I can open up another PR to help to migrate this project into non-Go workspace one.

I added several other common and widely used .gitignore entries for binaries like sample-app, and commonly leaking credentials, as well as the .DS_Store for macOS users.

[nirga]

Thanks @nekomeowww!