Add josm scheme link to edit menu

[AntonKhorev]

On Android, Vespucci is registered for josm: links: https://vespucci.io/tutorials/vespucci_intents/#supported-intents

This provides an option to run Vespucci as requested by #3836. Fixes #5326.

I'm not yet making it selectable as a preference because we might want to have this equivalent to remote control on Android. That's what #1478 tried to do. The reasoning for this is probably the following. Let's say I set my preferred editor to remote control. Then I open the website on Android. Surely remote control is not going to work there as is. But I still want something to happen when I press edit. How about this thing that I added in this PR?

But there are also reasons against combining this with remote control:

• it requires detecting the OS, something we'd rather not do
• technically there's nothing Android-specific in josm: links
• what if we're on iPhone or something else where http://127.0.0.1:8111 doesn't work but josm: does?
• what if we're on something where http://127.0.0.1:8111 does work, and we want both it and josm:?

[tomhughes]

Why on earth is it josm: though...

[AntonKhorev]

Probably because it supports some of the commands that remote control also supports, and remote control is mostly a JOSM thing.

[matkoniecz]

it requires detecting the OS, something we'd rather not do

is it problematic for some reason? (is there really no reliable way to do it?)

[AntonKhorev]

I tried registering this script as a josm: protocol handler on a desktop with JOSM remote control running, seems to work:

#!/usr/bin/perl

use LWP::Simple;
my $url = $ARGV[0];
$url =~ s{^josm:}{http://127.0.0.1:8111};
get $url;