Update docs

docs/c-interoperability.md

@@ -8,9 +8,12 @@ make this possible, there are a few tools available.
 
 In order to link against a compiled shared library, you can use `use libfoo.so`
 to cause Tomo to add `-l:libfoo.so` to the linker flags when compiling your
-final executable. You can also use `use <foo.h>` or `use "foo.h"` to cause Tomo
+final executable. You can also use `use <foo.h>` or `use ./foo.h` to cause Tomo
 to insert a corresponding `#include` when compiling your code.
 
+You can also `use ./foo.c` or `use ./foo.S` to use C or assembly source files
+from inside a Tomo source file.
+
 ## Inline C Code
 
 As a final escape hatch, you can use `inline C` to add code that will be put,