fix: all: fixes to get emacs-chess working on 30.2

- added lexical-binding headers to all source files
- replaced make-variable-buffer-local with defvar-local throughout source code
- replaced deprecated cl library with cl-lib, including replacing assert with cl-assert to emacs-chess-steps.el
- added proper headers and footers to test files when missing
- populated chess images and chess sounds directory
- fixed defcustom calling directory-files without error handling.
  xboard installation no longer required.

2 files changed, 0 insertions, 0 deletions

diff --git a/sounds b/sounds
deleted file mode 160000
-Subproject ad8eb2edd49d53b748d5e78958128c1996cfa4a
diff --git a/sounds/c5.wav b/sounds/c5.wav
new file mode 100644
index 0000000..e343091
--- /dev/null
+++ b/sounds/c5.wav