Doesn't work with pnpm v7

[zkochan]

I just release pnpm v7.0.0-alpha.0 and for some reason it doesn't work with this action. Looks like it doesn't appear in the PATH. Might be related to this: pnpm/pnpm#4280

[KSXGitHub]

This action only calls the self installer provided by pnpm:

action-setup/src/install-pnpm/run.ts

Lines 8 to 29 in 7c4472d

	export async function runSelfInstaller(inputs: Inputs): Promise<number> {
	const { version, dest } = inputs
	const target = version ? `pnpm@${version}` : 'pnpm'
	const pkgJson = join(dest, 'package.json')
	await remove(dest)
	await ensureFile(pkgJson)
	await writeFile(pkgJson, JSON.stringify({ private: true }))
	const cp = spawn(execPath, ['-', 'install', target, '--no-lockfile'], {
	cwd: dest,
	stdio: ['pipe', 'inherit', 'inherit'],
	})
	const response = await fetch('https://pnpm.js.org/pnpm.js')
	response.body.pipe(cp.stdin)
	return new Promise((resolve, reject) => {
	cp.on('error', reject)
	cp.on('close', resolve)
	})
	}

[zkochan]

Fixed in v2.1.0 via #29