install pnpm in all jobs #9

Job	Run time
test-node-web5 (20, ubuntu-latest)	1m 48s
test-electron (windows-latest)	4m 45s
test-node-web5 (18, ubuntu-latest)	1m 54s
test-rn-ios	3m 35s
test-electron (ubuntu-latest)	2m 34s
test-browsers (desktop-safari)	4m 15s
test-electron (macos-latest)	5m 56s
test-browsers (desktop-chrome)	4m 30s
test-browsers (desktop-firefox)	4m 24s
test-browsers (desktop-edge)	4m 3s
test-browsers (mobile-safari)	4m 13s
test-browsers (mobile-chrome)	4m 7s
	46m 4s

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