docs: package managers CLI instructions across OS's

[juliolmuller]

The duplicate npm commands in the documentation draw my attention and I saw some of the CLI commands uses the @commitlint/{cli,config-conventional} syntax. In the case of npm (for Windows), however, it uses the good old verbose one (@commitlint/cli @commitlint/config-conventional).

However, this differentiation does not only apply to npm, but for other package managers like yarn and pnpm in Windows as well. So, for simplification and consistency, I'd suggest defining a single command for each package manager and use the syntax compatible across operating systems.