Add support for FLAC keysounds

[dtinth]

Changelog

Added support for .flac keysounds in custom songs. Note that this only works on browsers that natively support FLAC files.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov-commenter]

Codecov Report

Base: 80.98% // Head: 80.99% // Increases project coverage by +0.00% :tada:

Coverage data is based on head (4936669) compared to base (a5af761). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #786 +/- ## ======================================= Coverage 80.98% 80.99% ======================================= Files 177 177 Lines 5270 5271 +1 Branches 240 240 ======================================= + Hits 4268 4269 +1 Misses 933 933 Partials 69 69 ``` | [Impacted Files](https://codecov.io/gh/bemusic/bemuse/pull/786?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bemusic) | Coverage Δ | | |---|---|---| | [bemuse/src/game/loaders/samples-loader.js](https://codecov.io/gh/bemusic/bemuse/pull/786/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bemusic#diff-YmVtdXNlL3NyYy9nYW1lL2xvYWRlcnMvc2FtcGxlcy1sb2FkZXIuanM=) | `97.29% <ø> (+0.07%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bemusic). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bemusic)

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