Add ext-ds extention support

[boskiv]

I'm trying to use ccxt php package in my application but it requires ext-ds php extension that i can't find in support list.
How we ca add it to official php buildpack?
https://pecl.php.net/package/ds

remote:  !     ERROR: Failed to install system packages!
remote:  !     
remote:  !     Your platform requirements (for runtimes and extensions) could
remote:  !     not be resolved to an installable set of dependencies, or a
remote:  !     platform package repository was unreachable.
remote:  !     
remote:  !     This usually means that you (or packages you are using) depend
remote:  !     on a combination of PHP versions and/or extensions that are
remote:  !     currently not available on Heroku.
remote:  !     
remote:  !     The following is the full output from the installation attempt:
remote:  !     
remote:  !     > Loading repositories with available runtimes and extensions
remote:  !     > Updating dependencies
remote:  !     > Your requirements could not be resolved to an installable set of packages.
remote:  !     > 
remote:  !     >   Problem 1
remote:  !     >     - composer.json/composer.lock requires ext-ds * -> no matching package found.
remote:  !     >   Problem 2
remote:  !     >     - Installation request for ccxt/ccxtpro 0.7.48 -> satisfiable by ccxt/ccxtpro[0.7.48].
remote:  !     >     - ccxt/ccxtpro 0.7.48 requires ext-ds * -> no matching package found.