[TRI-1794] Digital Ocean self-hosting docs

[matt-aitken]

A customer kindly provided this information when they got Trigger.dev working on Digital Ocean:

Everything is the exact same as fly except for needing to have your own dockerhub image (perhaps fixed in the future) and needing to set NODE_TLS_REJECT_UNAUTHORIZED='0'. Without that env var, you get the following error from graphile:

[2023-12-22 10:08:56] Error: self-signed certificate in certificate chain
[2023-12-22 10:08:56]     at TLSSocket.onConnectSecure (node:_tls_wrap:1600:34)
[2023-12-22 10:08:56]     at TLSSocket.emit (node:events:517:28)
[2023-12-22 10:08:56]     at TLSSocket._finishInit (node:_tls_wrap:1017:8)
[2023-12-22 10:08:56]     at ssl.onhandshakedone (node:_tls_wrap:803:12) {
[2023-12-22 10:08:56]   code: 'SELF_SIGNED_CERT_IN_CHAIN'
[2023-12-22 10:08:56] }

_TRI-1794