add nixos to readme

[sa7mon]

Closes #138

[github-actions]

Package	Line Rate	Complexity	Health
github.com/sa7mon/s3scanner	0%	0	❌
github.com/sa7mon/s3scanner/bucket	91%	0	✔
github.com/sa7mon/s3scanner/cmd/mqingest	0%	0	❌
github.com/sa7mon/s3scanner/cmd/regioncheck	55%	0	➖
github.com/sa7mon/s3scanner/cmd/s3scanner	19%	0	❌
github.com/sa7mon/s3scanner/collection	0%	0	❌
github.com/sa7mon/s3scanner/db	73%	0	➖
github.com/sa7mon/s3scanner/log	0%	0	❌
github.com/sa7mon/s3scanner/mq	71%	0	➖
github.com/sa7mon/s3scanner/permission	28%	0	❌
github.com/sa7mon/s3scanner/provider	79%	0	✔
github.com/sa7mon/s3scanner/provider/clientmap	100%	0	✔
github.com/sa7mon/s3scanner/worker	49%	0	❌
Summary	58% (622 / 1077)	0	➖