Add CPU requirements to running nodes

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A user complained about Bootstrap not working: https://nem2.slack.com/archives/C9YKR0EUX/p1616384908139900

broker          /symbol-commands/start.sh: line 126:    10 Illegal instruction     (core dumped) $catapultAppFolder/bin/$processName "$config"\
node            /symbol-commands/start.sh: line 126:    10 Illegal instruction     (core dumped) $catapultAppFolder/bin/$processName "$config"\
broker          /symbol-commands/start.sh: line 126:    11 Illegal instruction     (core dumped) $catapultAppFolder/bin/$processName "$config"\

Errors seem to indicate unsupported CPUs, so we should document these requirements.

Related: https://github.com/nemtech/symbol-bootstrap/issues/207#issuecomment-804547111

[segfaultxavi]

More info: https://discord.com/channels/856325968096133191/887352684066259024/919892143911362572

we publish images only for westmere and skylake you should be able to build for any modern x64 ofc (all linux, mac, windows should do) on top of that it's possible to build for aarch64 (although we do not provide images / you're on your own)