FEATURE: Implement major enhancements for performance and usability

This commit introduces several key improvements:

- Parallel Processing: Utilizes `concurrent.futures.ThreadPoolExecutor`
  to process multiple video files simultaneously, significantly
  speeding up batch operations. A new `--jobs` flag allows
  customization of worker threads.

- Progress Bar: Integrates `tqdm` to display a real-time progress
  bar, providing users with feedback on the status, ETA, and
  speed of the transcoding process.

- Dry Run Mode: Adds a `--dry-run` command-line flag. When active,
  the script analyzes files and reports intended actions (transcode,
  copy, skip) without making any actual changes to the files,
  allowing users to preview operations.

- Graceful Exit (Ctrl+C): Implements robust handling of
  KeyboardInterrupt. FFmpeg now writes to temporary files (`.tmp`),
  which are only renamed upon successful completion. If the process
  is interrupted or an error occurs, these temporary files are
  automatically cleaned up, preventing corrupt or partial output.

- Dependencies: Adds `tqdm` to `install_requires` in `setup.cfg`.
- Version: Bumps project version to 0.3.0 to reflect these
  significant feature additions.

FIX: Actually Skip video files where no transcoding is needed.

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = surround-to-eac3
-version = 0.2.1
+version = 0.3.0
 author = Jonathan Rampersad
 author_email = jonathan@jono-rams.work
 description = A CLI tool to transcode 5.1 audio in video files to E-AC3.
@@ -17,6 +17,8 @@ package_dir =
     = src
 packages = find:
 python_requires = >=3.10
+install_requires = 
+    tqdm
 
 [options.packages.find]
 where=src