chore: add a script to update BSL license change date

scripts/update-bsl-license-convert-year.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+CONVERT_DATE="$(date -d "+4 years" '+%Y-%m-%d')"
+NEWTEXT="Change Date:          $CONVERT_DATE"
+
+update() {
+    local file="$1"
+    sed -E "s#(^Change Date: *)(.*)#\1$CONVERT_DATE#g" -i "$file"
+}
+
+while read -r file; do
+    if [[ $file != *BSL.txt ]]; then
+        ## Ignore other files
+        continue
+    fi
+    update "$file"
+done < <(git ls-files)