Configurable capture backend (#150)

capture backend can now be configured via the `capture_backend` cli argument / config entry

src/capture/macos.rs

@@ -1,7 +1,7 @@
+use crate::capture::error::MacOSInputCaptureCreationError;
 use crate::capture::InputCapture;
 use crate::client::{ClientEvent, ClientHandle};
 use crate::event::Event;
-use anyhow::{anyhow, Result};
 use futures_core::Stream;
 use std::task::{Context, Poll};
 use std::{io, pin::Pin};
@@ -9,8 +9,8 @@ use std::{io, pin::Pin};
 pub struct MacOSInputCapture;
 
 impl MacOSInputCapture {
-    pub fn new() -> Result<Self> {
-        Err(anyhow!("not yet implemented"))
+    pub fn new() -> std::result::Result<Self, MacOSInputCaptureCreationError> {
+        Err(MacOSInputCaptureCreationError::NotImplemented)
     }
 }