Add note for CPU support in docs - Apple Sillicon compatibility

[sturmenta]

In the documentation it is clearly stated that only x86_64 processors are supported for Akash deployments

But

From a mac with m1 processor I was able to run my deploys to akash network indicating at the moment of building the docker image that the target platform is linux/amd64.

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without specifying that the target platform is linux/amd64 my images did not work

after specifying this my docker images work on akash network