Allow ~ in keys for escaped json pointer characters

Signed-off-by: Taylor Gray <tylgry@amazon.com>

Author: graytaylor0

data-prepper-api/src/main/java/org/opensearch/dataprepper/model/event/JacksonEventKey.java

@@ -159,6 +159,7 @@ private static boolean isValidKey(final String key) {
                     || c == '-'
                     || c == '_'
                     || c == '@'
+                    || c == '~'
                     || c == '/'
                     || c == '['
                     || c == ']')) {