chore(documentation): network flow documentation

[Jose-Matsuda]

Closes
https://github.com/StatCan/aaw-private/issues/128

Note that this documentation will need to be updated as the ### Allow Connection to internal application in an already peered network does not fully work

[Souheil-Yazji]

LGTM

[Jose-Matsuda]

I've made more changes in response to Pat's comments and I think it's in a good state.
The other thing mentioned on slack was only having main topics of;

1. Adding Application Firewall Rule
2. Adding Network Firewall Rule
3. DNS

but admittedly, I've grown attached to my version and I think it serves the purpose of having an obvious example that developers who may not be too into the weeds (like myself) would gravitate to more.

[chuckbelisle]

lgtm, thank @vexingly for the comments and prior review. Also thank you to @Jose-Matsuda for creating this documentation.