Docs: Specify the string length limitation when verifying paste patterns

Hello,
While integrating my own service with the embed tool, I noticed that there is a 450-character limitation for paste patterns.
[Link to the relevant code line](https://github.com/codex-team/editor.js/blob/631340912e7a1b3db1e114e930ddf1e97ec4ea61/src/components/modules/paste.ts#L113)
I have opened an issue: [GitHub Issue #135](https://github.com/editor-js/embed/issues/135)
I am not sure if this limitation is intentional or not, but I think it would be beneficial to have the ability to adjust this limit.

Start at src/components/modules/paste.ts around line 113 and review the linked embed issue for context. Update the appropriate documentation to state the paste-pattern string-length limitation, with the work complete when readers can find the 450-character limit and understand its scope.

Vom Indexierungsmodell aus dem Issue-Text verfasst.