Add periodictable recipe

recipes/periodictable/recipe.sh

+GIT=https://github.com/xtibor/periodictable.git
+BINDIR="/ui/bin"
+
+function recipe_stage {
+    mkdir -pv "$1/ui/apps"
+    cp -v pkg/manifest "$1/ui/apps/periodictable"
+    mkdir -pv "$1/ui/icons"
+    cp -v pkg/icon.png "$1/ui/icons/periodictable.png"
+}
+