added service and timer files, aswell as Arch PKGBUILD

updated version in main.cpp to be a dependency from cmake

PKGBUILD

@@ -0,0 +1,24 @@
+# PKGBUILD
+pkgname=arduino_watchdog
+pkgrel=1
+pkgdesc="Arduino based external watchdog to keep server online"
+arch=('any')
+license=('MIT')
+makedepends=('cmake: build system used')
+depends=('systemd>=257.6')
+source=('git://git.server.4zellen.se/Zacharias/home-lab_watchdog_keepalive.git')
+maintainer="Zacharias Zellén <zacharias@4zellen.se>"
+url="https://git.server.4zellen.se/Zacharias/home-lab_watchdog_keepalive.git"
+
+
+build() {
+    cd "$srcdir/home-lab_watchdog_keepalive"
+
+    cmake -B build -S . -DVERSION="\"$pkgver\""
+    make -C build
+}
+
+pkgver() {
+  cd "$srcdir/home-lab_watchdog_keepalive"
+  git describe --tags | sed 's/^v//;s/-/+/g'
+}