chore: add note for supporting only amd64 architecture at the moment (#720)

Signed-off-by: Trong Nhan Mai <trong.nhan.mai@oracle.com>

Author: Trong Nhan Mai

docs/source/pages/installation.rst

@@ -15,6 +15,7 @@ Prerequisites
   - Macaron has been tested with ``bash 5.1.16(1)-release``.
 
 - Docker (or docker equivalent for your host OS) must be installed, with a docker command line equivalent to Docker 17.06 (Oracle Container Runtime 19.03) and the user should be a member of the operating system group ``docker`` (to run Docker in `rootless mode <https://docs.docker.com/engine/security/rootless/>`_).
+- We only support ``amd64`` / ``x86_64`` platforms at the moment.
 
 .. _download-macaron: