Add .clang-format

Most options are configured to keep most of the current style.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

scripts/clang-format.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: GPL-3.0-only
+
+FILES=($(git ls-files '*.[ch]'))
+
+FMT_OPTS=(
+    "-style=file"
+    "--fallback-style=none"
+    "--Werror"
+)
+
+if [[ "$1" = "apply" ]]; then
+    clang-format "${FMT_OPTS[@]}" -i "${FILES[@]}"
+else
+    clang-format "${FMT_OPTS[@]}" --dry-run "${FILES[@]}"
+fi