doc: unicode extension does not work with load_extension()

docs/unicode.md

@@ -10,6 +10,12 @@ Overrides the default NOCASE case-insensitive collation sequence to support UTF-
 
 Has no external dependencies (like libicu). Adapted from [sqlite3_unicode](https://github.com/Zensey/sqlite3_unicode) by Anton Litvinov.
 
+⚠️ This extension cannot be loaded via `load_extension()` SQL function due to SQLite restrictions. Quoting the [docs](https://sqlite.org/lang_corefunc.html#load_extension):
+
+> The load_extension() function will fail if the extension attempts to modify or delete an SQL function or collating sequence. The extension can add new functions or collating sequences, but cannot modify or delete existing functions or collating sequences because those functions and/or collating sequences might be used elsewhere in the currently running SQL statement. To load an extension that changes or deletes functions or collating sequences, use the `sqlite3_load_extension()` C-language API.
+
+It works via SQLite CLI `.load` command, though.
+
 ## Usage
 
 Before: