[proposal] add `monero_node:` to the URI spec

[nahuhh]

Cake Wallet and the Monero Nodo project currently utilize a URI for sharing node parameters, but the URI doesn't match the style of other monero based URIs.

This proposal is to standardize the URI for adding/sharing nodes (so all interested parties can be compatible).

The proposed URI is:

monero_node:[host=]<host>?port=<port>[&protocol=<string>][&username=<username>&password=<password>][&trusted=<bool>][&label=<label>] 

Everything in square brackets is optional.

The below would be appended to the URI doc here

---

Node Sharing Scheme

The following scheme is proposed as a means of sharing node parameters.

monero_node:[host=]<host>?port=<port>[&param=<param>][&param2=<param2]

Parameter	Type	Optional	Requires	Description
host	String	n	port	Domain or IP address of node
port	String	n	host	Port which the RPC is bound
protocol	String	y	host,port	Set transport protocol
username	String	y	host,port	Username of the RPC login
password	String	y	host,port	Password of the RPC login
trusted	Bool	y	host,port	Mark the node as trusted
label	String	y	host,port	Specify a label for the node

The resulting URI for sharing node parameters may look like this:

monero_node:192.168.1.1?port=18089&protocol=https&trusted=true

or

monero_node:192.168.1.1?port=18089&username=monero&password=xmr&trusted=true&label=My%20Node

[acx-usernamealreadyused]

I support this proposal.

The only concern I have is with the tls field - do you think it might be a good idea to replace it with [&schema=http/https] (or something like protocol) instead?
It seems to me that this would make the uri more generic, allowing us to use protocols other than http(s) in the future.

[detherminal]

Needed for better UX, I support this.