feat(wm): add workspace rules

This feature allows users to specify which monitor/workspace an
application's window, identified either by executable name or window
class name, should be assigned to.

A new fn, WindowManager.enforce_workspace_rules, is called whenever a
new rule is added, and periodically whenever an event is processed by
komorebi (just after orphan windows are repead, before the matching and
processing of the specific event).

Both class and exe identifiers are stored in the same HashMap for the
sake of simplicity, as I couldn't think of any situations where there
might be a clash between the two identifiers.

Did some light refactoring of window_manager.rs to make the new()
constructor a static method on the WindowManager struct.

Also fixed a bug in Workspace.new_container_for_window where the focused
index was not getting set correctly when the workspace had no
containers.

README.md

@@ -118,7 +118,7 @@ Once `komorebi` is running, you can execute the `komorebi.sample.ahk` script to
 If you have AutoHotKey installed and a `komorebi.ahk` file in your home directory (run `$Env:UserProfile` at a
 PowerShell prompt to find your home directory), `komorebi` will automatically try to load it when starting.
 
-There is also tentative support for loading a AutoHotKey v2, if the file is named `komorebi.ahk2` and
+There is also tentative support for loading a AutoHotKey v2 files, if the file is named `komorebi.ahk2` and
 the `AutoHotKey64.exe` executable for AutoHotKey v2 is in your `Path`. If both `komorebi.ahk` and `komorebi.ahk2` files
 exist in your home directory, only `komorebi.ahk` will be loaded. An example of an AutoHotKey v2 configuration file
 for _komorebi_ can be found [here](https://gist.github.com/crosstyan/dafacc0778dabf693ce9236c57b201cd).
@@ -182,6 +182,7 @@ restore-windows              Restore all hidden windows (debugging command)
 reload-configuration         Reload ~/komorebi.ahk (if it exists)
 watch-configuration          Toggle the automatic reloading of ~/komorebi.ahk (if it exists)
 float-rule                   Add a rule to always float the specified application
+workspace-rule               Add a rule to associate an application with a workspace
 identify-tray-application    Identify an application that closes to the system tray
 focus-follows-mouse          Enable or disable focus follows mouse for the operating system
 help                         Print this message or the help of the given subcommand(s)
@@ -206,10 +207,9 @@ help                         Print this message or the help of the given subcomm
 - [x] BSP tree layout
 - [x] Flip BSP tree layout horizontally or vertically
 - [x] Equal-width, max-height column layout
-- [x] Floating rules based on exe name
-- [x] Floating rules based on window title
-- [x] Floating rules based on window class
-- [x] Identify 'close/minimize to tray' applications
+- [x] Floating rules based on exe name, window title and class
+- [x] Workspace rules based on exe name and window class
+- [x] Identify 'close/minimize to tray' applications by exe name and class
 - [x] Toggle floating windows
 - [x] Toggle monocle window
 - [x] Toggle native maximization