new: add ui file_transfer

[nick1udwig]

Problem

We need more templates. #69

Solution

Add UI-enabled file_transfer.

Docs Update

Corresponding docs PR

Notes

Not quite working properly. I can query files from another node, but when I try to fetch a file I get

3️⃣  Mon 2/19 14:43 event loop: got message: {
    id: 11456763969558331655,
    source: fake.os@http_server:distro:sys,
    target: fake.os@foo:foo:template.os,
    rsvp: None,
    message: Request(
        inherit: false,
        expects_response: None,
        body: {"WebSocketPush":{"channel_id":258709850,"message_type":"Binary"}},
        metadata: None,
        capabilities: [],
    ),
    blob: true,
}
3️⃣  Mon 2/19 14:43 event loop: got message: {
    id: 16346904803609623827,
    source: fake.os@foo:foo:template.os,
    target: fake.os@vfs:distro:sys,
    rsvp: fake.os@foo:foo:template.os,
    message: Request(
        inherit: false,
        expects_response: Some(5),
        body: {"action":"ReadDir","path":"/foo:template.os/files"},
        metadata: None,
        capabilities: [],
    ),
    blob: false,
}
3️⃣  Mon 2/19 14:43 event loop: got message: {
    id: 16346904803609623827,
    source: fake.os@vfs:distro:sys,
    target: fake.os@foo:foo:template.os,
    rsvp: None,
    message: Response(
        inherit: false,
        body: {"ReadDir":[]},
        metadata: None,
        context: None,
        capabilities: [],
    ),
    blob: false,
}

and the UI sits at 0% forever without ever sending a request to the other node.