docs(mkdocs): add common workflows section

docs/common-workflows/focus-follows-mouse.md

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+# Focus Follows Mouse
+
+`komorebi` supports two focus-follows-mouse implementations; the native Windows
+Xmouse implementation, which treats the desktop, the task bar, and the system
+tray as windows and switches focus to them eagerly, and a custom `komorebi`
+implementation, which only considers windows managed by `komorebi` as valid
+targets to switch focus to when moving the mouse.
+
+To enable the `komorebi` implementation you must start the process with the
+`--ffm` flag to explicitly enable the feature. This is because the mouse
+tracking required for this feature significantly increases the CPU usage of the
+process (on my machine, it jumps from <1% to ~4~), and this CPU increase
+persists regardless of whether focus-follows-mouse is enabled or disabled at
+any given time via `komorebic`'s configuration commands.
+
+If the `komorebi` process has been started with the `--ffm` flag, you can
+enable focus follows mouse behaviour in the `komorebi.json` configuration file.
+
+```json
+{
+  "focus_follows_mouse": "Komorebi"
+}
+```
+
+When calling any of the `komorebic` commands related to focus-follows-mouse
+functionality, the `windows` implementation will be chosen as the default
+implementation. You can optionally specify the `komorebi` implementation by
+passing it as an argument to the `--implementation` flag:
+
+```powershell
+komorebic.exe toggle-focus-follows-mouse --implementation komorebi
+```
+
+