fix: SC2324 shellcheck (#327)

Fix SC2324 shellcheck warning by adding -i to indicate var type of
integer and tidy up the formatting.

scripts/version-sync.sh

@@ -13,12 +13,12 @@ function usage {
 }
 
 function getopts-extra () {
-    declare i=1
+    declare -i i=1
     # if the next argument is not an option, then append it to array OPTARG
     while [[ ${OPTIND} -le $# && ${!OPTIND:0:1} != '-' ]]; do
         OPTARG[i]=${!OPTIND}
-        i+=1
-        OPTIND+=1
+        ((i += 1))
+        ((OPTIND += 1))
     done
 }