Add keepalive "heartbeat" message to Fast Refresh connections #755

Job	Run time
Type check, lint, smoke test	49s
Tests with coverage	1m 46s
test (macos-latest, 20.19.4) / Tests [Node.js 20.19.4, macos-latest, Using yarn.lock]	1m 21s
test (macos-latest, lts/-1) / Tests [Node.js lts/-1, macos-latest, Using yarn.lock]	1m 16s
test (ubuntu-latest, lts/-1) / Tests [Node.js lts/-1, ubuntu-latest, Using yarn.lock]	1m 1s
test (ubuntu-latest, latest) / Tests [Node.js latest, ubuntu-latest, Using yarn.lock]	1m 0s
test (macos-latest, latest) / Tests [Node.js latest, macos-latest, Using yarn.lock]	1m 8s
test (windows-latest, lts/-1) / Tests [Node.js lts/-1, windows-latest, Using yarn.lock]	1m 34s
test (windows-latest, 20.19.4) / Tests [Node.js 20.19.4, windows-latest, Using yarn.lock]	1m 37s
test (ubuntu-latest, 20.19.4) / Tests [Node.js 20.19.4, ubuntu-latest, Using yarn.lock]	1m 11s
test (windows-latest, latest) / Tests [Node.js latest, windows-latest, Using yarn.lock]	1m 35s
test (macos-latest, lts/) / Tests [Node.js lts/, macos-latest, Using yarn.lock]	1m 9s
test (windows-latest, lts/) / Tests [Node.js lts/, windows-latest, Using yarn.lock]	1m 37s
test (ubuntu-latest, lts/) / Tests [Node.js lts/, ubuntu-latest, Using yarn.lock]	55s
Deploy	0s
	17m 59s

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