PEP 818: Add "Emscripten-forge supports this pep" to motivation (#5159)

Author: hoodmane

peps/pep-0818.rst

@@ -64,6 +64,17 @@ interface, it will be possible to support ``urllib`` on Emscripten. Downstream,
 supporting ``urllib3``, ``aiohttp``, and ``httpx`` requires the foreign function
 interface.
 
+The fact that the Pyodide foreign function interface is coupled to Pyodide
+creates problems for other Emscripten-CPython distributions. For instance,
+`Emscripten-forge`_ is a project that provides conda recipes for the Emscripten
+platform. They have to reimplement the Pyodide foreign function interface in
+order to support downstream packages that use it. Their reimplementation is
+slower and has various minor incompatibilities. For this reason, the
+Emscripten-force maintainers strongly support adding Pyodide's interface to
+CPython.
+
+..  _Emscripten-forge: https://emscripten-forge.org/
+
 In order to keep the length of this PEP reasonable, we focus on the "core" of
 the foreign function interface. The JavaScript interface for managing the Python
 runtime is left to a future PEP.