Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires fig-r/psr2r-sniffer dev-next -> satisfiable by fig-r/psr2r-sniffer[dev-next].
- fig-r/psr2r-sniffer dev-next requires php-collective/code-sniffer dev-next -> found php-collective/code-sniffer[dev-next] but it does not match your minimum-stability.