### Description
Added support for previewing FLAC files in the web interface, provided
in #509 by marmotte32 on Github in the comments for this issue.
I have tested this against a script-installed copy of 4.2.0, and FLAC
preview is working, although auto-play isn't. I haven't tested to
confirm if this behavior matches MP3 and OGG uploads.
**This is a new feature**:
_Do the changes in this PR implement a new feature?_
**I have updated the documentation to reflect these changes**:
No changes needed; this bug is a missing file format in preview, and it
requires no updates to the documentation.
### Testing Notes
**What I did:**
I installed a LibreTime 4.2.0 system using the default installation
script against a fully-updated, brand new Debian 11 system. I logged
into the web interface, uploaded some FLAC files, and attempted to
preview them. They failed to preview.
I then replaced the preview_jplayer.js file with the contents in this PR
and then refreshed the page. I was able to preview the FLAC files and
hear the results in my local browser audio output.
**How you can replicate my testing:**
Perform the same steps above, or replace the same file in the
libretime_legacy_1 docker image to see the same results.
### **Links**
Closes: #509
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Co-authored-by: Kyle Robbertze <kyle@paddatrapper.com>
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