Add #include <algorithm> to fix building with gcc 14
With gcc 14 some C++ Standard Library headers have been changed to no
longer include other headers that were used internally by the library.
In libdatachannel's case it is the <algorithm> header.
GCC 14 porting guide: https://gcc.gnu.org/gcc-14/porting_to.html#header-dep-changes
Signed-off-by: Kostadin Shishmanov <[email protected]>