System.IO.DirectoryNotFoundException on first dotnet run

Hi @AngelMunoz I've been brought here from https://github.com/SAFE-Stack/SAFE-template/issues/532 and wanted to give Perla a shot. For some reason when I do `dotnet run` on a fresh repository, following exception is thrown:

```
...
server: /Users/theimowski/oss/AngelMunoz/SafePerla/src/Server> dotnet watch run
client: /Users/theimowski/oss/AngelMunoz/SafePerla/src/Client> dotnet perla serve
/Users/theimowski/oss/AngelMunoz/SafePerla/src/Server> "dotnet" watch run (In: false, Out: true, Err: true)
/Users/theimowski/oss/AngelMunoz/SafePerla/src/Client> "dotnet" perla serve (In: false, Out: true, Err: true)
client: Perla: Checking whether esbuild is present...
client: Perla: esbuild is present.
client: Perla:Serve: Starting Dev Server
client: Perla:Serve: Starting Fable
client: Unhandled exception. System.IO.DirectoryNotFoundException: /Users/theimowski/oss/AngelMunoz/SafePerla/src/Client/output/
client: at Microsoft.Extensions.FileProviders.PhysicalFileProvider..ctor(String root, ExclusionFilters filters)
client: at Perla.Lib.Server.devServer(PerlaConfig config) in /Users/tuna/repos/Perla/src/Perla.Lib/Server.fs:line 656
client: at Perla.Lib.Server.startServer(PerlaConfig config) in /Users/tuna/repos/Perla/src/Perla.Lib/Server.fs:line 706
client: at Perla.Lib.Server.serverActions@724-1.Invoke(Unit unitVar) in /Users/tuna/repos/Perla/src/Perla.Lib/Server.fs:line 725
client: at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvoke[T,TResult](AsyncActivation`1 ctxt, TResult result1, FSharpFunc`2 part2) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 508
client: at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 112
client: --- End of stack trace from previous location ---
client: at Microsoft.FSharp.Control.AsyncPrimitives.Start@1167-1.Invoke(ExceptionDispatchInfo edi) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 1167
client: at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 112
client: at .$Async.clo@193-15.Invoke(Object o) in D:\a\_work\1\s\src\FSharp.Core\async.fs:line 195
client: at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
client: at System.Threading.ThreadPoolWorkQueue.Dispatch()
client: at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
client: at System.Threading.Thread.StartCallback()
server: dotnet watch 🚀 Started
...
```

interestingly, after I cancel the run, the directory is there and subsequent `dotnet run` works fine - smells like some kind of race condition possibly?
I'm using MacOS FWIW

Reproduce the failure with `dotnet run` on a fresh repository, then inspect `src/Perla.Lib/Server.fs` around lines 656 and 706, where the stack trace enters `devServer` and `startServer`. Done means the first run starts without `DirectoryNotFoundException` and subsequent runs continue to work without cancelling the process.

Written by the indexing model from the issue text.