Check file type before decoding

[Borketh]

Fred v2.25.0
UnicodeDecodeError exception handled in on_message in Satisfactory Modding: #Unable to open SMM; mods not loading (<#1343187664756674601>)

'utf-8' codec can't decode byte 0xf4 in position 27: invalid continuation byte

  File "/app/venv/lib/python3.12/site-packages/nextcord/client.py", line 527, in _run_event
    await coro(*args, **kwargs)
  File "/app/fred/fred.py", line 298, in on_message
    _reacted = await self.Crashes.process_message(message)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/fred/cogs/crashes.py", line 365, in process_message
    raise ex
  File "/app/fred/cogs/crashes.py", line 354, in process_message
    jobs.extend((task_group.create_task(job) for job in self._get_file_jobs(name, file)))
  File "/app/fred/cogs/crashes.py", line 354, in <genexpr>
    jobs.extend((task_group.create_task(job) for job in self._get_file_jobs(name, file)))
                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/fred/cogs/crashes.py", line 265, in _get_file_jobs
    yield self.process_text(str(file.read().decode()), filename=filename)
                                ^^^^^^^^^^^^^^^^^^^^