quick and dirty /join command

[ara4n]

In order to avoid getting crucified by the matrix community for shipping a matrix client which can't join rooms by alias (somewhat like shipping a web browser without a url bar), here's a quick go at adding a /join slash command as an easter-egg for powerusers.

I've probably done it wrong, but:

• The slashcommand code is on the TimelineViewModel for now, alongside the logic which turns composer input into sending messages.
• In order to actually open the room which you then join, it uses openURL - but it has to use the one inside the SwiftUI environment given that's where the local app routing happens (otherwise it goes and opens it in an external app). So I pull an openURL handler in a closure through in the state bindings from the TimelineView to the TimelineViewModel. I assume there may be a fancier way to get SwiftUI to handle the openURL, but this seems to work fine even if it's a bit ugly. (How come AppMediator has a useless open() method which doesn't use the App's openURL impl?)

Pull Request Checklist

• I read the contributing guide.
• Pull request contains a changelog label.

[github-actions]

	Warnings
⚠️	Some of the commits are missing ticket numbers. Please consider squashing all commits that don't have a tracking number.
⚠️	Please add a sign-off to either the PR description or to the commits themselves.
⚠️	You seem to have made changes to views. Please consider adding screenshots.

Generated by 🚫 Danger Swift against 9fdf1f2

[codecov]

Codecov Report

Attention: Patch coverage is 18.75000% with 26 lines in your changes missing coverage. Please review.

Project coverage is 77.34%. Comparing base (943f33b) to head (9fdf1f2).
Report is 1 commits behind head on develop.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...X/Sources/Screens/Timeline/TimelineViewModel.swift	7.14%	26 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3288      +/-   ##
===========================================
- Coverage    77.37%   77.34%   -0.03%     
===========================================
  Files          735      735              
  Lines        59446    59475      +29     
===========================================
+ Hits         45995    46001       +6     
- Misses       13451    13474      +23     

Flag	Coverage Δ
unittests	68.68% <18.75%> (-0.03%)	⬇️

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[pixlwave]

LGTM 👍

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud