createkeyboard: do not segfault if xkb_keymap_new_from_names returns NULL

Passing NULL to wlr_keyboard_set_keymap results in a segfault.
Example:

  Thread 1 "dwl" received signal SIGSEGV, Segmentation fault.
  0x00007ffff7e49b64 in xkb_keymap_ref () from /usr/lib/libxkbcommon.so.0
  (gdb) bt
  #0  0x00007ffff7e49b64 in xkb_keymap_ref () at /usr/lib/libxkbcommon.so.0
  #1  0x00007ffff7f06389 in wlr_keyboard_set_keymap () at /usr/lib/libwlroots.so.11
  #2  0x000055555555bc54 in createkeyboard ()
  #3  0x000055555555c283 in inputdevice ()
  #4  0x00007ffff7e8101e in wl_signal_emit_mutable () at /usr/lib/libwayland-server.so.0
  #5  0x00007ffff7e8101e in wl_signal_emit_mutable () at /usr/lib/libwayland-server.so.0
  #6  0x00007ffff7edb52c in  () at /usr/lib/libwlroots.so.11
  #7  0x00007ffff7ee44b6 in  () at /usr/lib/libwlroots.so.11
  #8  0x000055555555fe66 in main ()

add a comment about chvt keybindings

Closes: https://github.com/djpohly/dwl/issues/427

clarify the dependencies needed by dwl

Note that previous df131cdb78c6e3e79c3fafa522f0e4f6b43d2ab4 libX11 headers
were also required for building (but not for runtime)

Also, I want to apologize to the packagers for do not list *all* the required
dependencies before.

update README.md

these things were changed in the code but not in the readme

check client is mapped before setting border color

For some reason brave configured for as a wayland client triggers this code on startup and segfaults.

Checking if the client is mapped fixes this, like with the previous fix for urgent border colour.

References: 887fde65a3010905aa10f373cfcfe540cfc1781e
Fixes: 72a7d78a1a7926a207539eb50f44b2e1eb089d49

use <xcb/xcb.h> instead of <X11/Xlib.h>

only set border color for urgent *and* mapped X11 clients

this fixes a segfault when the client emits .set_hints but it's not mapped

Fixes: 72a7d78a1a7926a207539eb50f44b2e1eb089d49

Revert "just add define"

I'm going to make some changes in the config file anyway

This reverts commit e5367753bb90add013ee5d170a110064298ac2c4.

add [-d] flag to enable debug logging

simplify setting the border color of clients

make the borders red borders for urgent clients

iirc this is the same behavior of dwm

use the same border colors as dwm

add missing url about the COLOR macro

add macro to configure colors

Closes: https://github.com/djpohly/dwl/issues/466

Check if c is fullscreen before reparenting it to LyrFloating

Closes: https://github.com/djpohly/dwl/issues/487

make sure that fullscreen clients are on the correct screen when isfloating is true

Bug: https://github.com/djpohly/dwl/issues/487

include dwl.desktop in the tarbal

allow specify DATADIR (to install desktop file)

Add desktop entry file

fix typo