fix: default mentions block @everyone; jump modal times out with the paginator

T2-10 (operator-ruled): mentions_allowed defaulted to AllowedMentions.all(),
so page content (often user-supplied) could ping @everyone/@here and the
paginator overrode a bot-wide none(). default to AllowedMentions(everyone=
False): user/role pings and the bot-wide settings still apply.

T2-11: JumpToPageModal used discord.py's default timeout=None, so every
dismissed modal stayed in ViewStore._modals forever, pinning its paginator.
pass the paginator's timeout.

Signed-off-by: disqualifier <dev@disqualifier.me>

README.md

@@ -149,7 +149,8 @@ through.
 - `timeout` — seconds before the view stops (default 180)
 - `delete_message_after` — delete the message on timeout
 - `per_page` — entries per page (default 1)
-- `mentions_allowed` — `AllowedMentions` for sends (default `.all()`)
+- `mentions_allowed` — `AllowedMentions` for sends (default `AllowedMentions(everyone=False)`:
+  no @everyone/@here, user/role pings and the bot-wide settings still apply)
 - `ephemeral` — send/edit ephemerally
 - `page_text` — format string for the jump button label
 - `emojis` — override navigation emojis