Implement configuration for keybindings

Keybinds go in a "keybinds" block and follow the format

<command> <modifiers> <keysym> <options>

But there's also a special "tag_bind" command that just takes modifiers
and one of set_output_tags, set_window_tags, toggle_output_tags, and
toggle_window_tags. It will automatically be used to loop through the
1-9 keys on tags 1<<0 to 1<<9, however, you can still implement those
commands individually if you want.

build.zig

@@ -48,6 +48,7 @@ pub fn build(b: *std.Build) void {
 
     exe.linkLibC();
     exe.linkSystemLibrary("wayland-client");
+    exe.linkSystemLibrary("xkbcommon");
 
     b.installArtifact(exe);
 
@@ -95,6 +96,7 @@ pub fn build(b: *std.Build) void {
 
     exe_check.linkLibC();
     exe_check.linkSystemLibrary("wayland-client");
+    exe_check.linkSystemLibrary("xkbcommon");
 
     const check = b.step("check", "Check if beanbag compiles");
     check.dependOn(&exe_check.step);