fix: transcoding file permissions

[shpingalet007]

Standards checklist:

• [x] The PR title is descriptive.
• [x] The PR doesn't replicate another PR which is already open.
• [x] The PR has self-explained commits history.
• [x] The code is mine, or it's from somewhere with an Apache-2.0 compatible license.
• [ ] The code is efficient, to the best of my ability, and does not waste computer resources.
• [ ] The code is stable, and I have tested it myself, to the best of my abilities.
• [x] If the code introduces new classes, methods, I provide a valid use case for all of them.

Changes:

• Fix final transcoding result not being renamed due to FS permission issues

Other changes:

• Replace NPM module html-minifier with html-minifier-terser due to CVE-2022-37620
• Replace deprecated fs.rmdirSync(...) with fs.rmSync(...)