Failure to load on Firefox when opening locally, GLSL files blocked due to MIME type

[slowriot]

Browser: Firefox Nightly 109.0a1 (2022-11-23) (64-bit) running on Debian

When I attempt to open index.html from the local filesystem, the page fails to load and browser console shows the following:

Loading script from file: URI (“file:///vis/Code/Shaders/Shared.glsl”) was blocked because its MIME type (“”) is not a valid JavaScript MIME type. [index.html](file:///home/slowriot/code/bigtort/include/remotery/vis/index.html)
Loading script from file: URI (“file:///vis/Code/Shaders/Grid.glsl”) was blocked because its MIME type (“”) is not a valid JavaScript MIME type. [index.html](file:///home/slowriot/code/bigtort/include/remotery/vis/index.html)
Loading script from file: URI (“file:///vis/Code/Shaders/Timeline.glsl”) was blocked because its MIME type (“”) is not a valid JavaScript MIME type. [index.html](file:///home/slowriot/code/bigtort/include/remotery/vis/index.html)
Loading script from file: URI (“file:///vis/Code/Shaders/Window.glsl”) was blocked because its MIME type (“”) is not a valid JavaScript MIME type. [index.html](file:///home/slowriot/code/bigtort/include/remotery/vis/index.html)

I should mention that opening in Chromium on the same system works fine.