This repo provides a JavaScript compiled (emscripten) version of libheif. The library is included as a submodule link, and compiled using the original repo scripts without modification to source or build scripts. You can get the compiled version from the releases page.
If you have found your way here while looking for a libheif version that you can install from npm, you are in the wrong place. Take a look at libheif-js instead.
Refer to the original license for licensing information.