Before this commit, passing a CoroutineContext with a Job to
ServiceImplBase's constructor ended up in the entirety of context's job
being cancelled (#302).

* Update README.md

* Update README.md

- Replaced YOUR_X_VERSION with variables
- Changed `protobuf.version` and `java.grpc.version` to fix the max supported values
- Added an `IMPORTANT:` comment to specify the max supported versions of protobuf and protobuf-kotlin

Co-authored-by: James Ward <james@jamesward.com>

As of rules_kotlin v1.5.0-beta-3, its JVM rules should be imported from
jvm.bzl, not kotlin.bzl, to prevent a noisy warning:
https://github.com/bazelbuild/rules_kotlin/blob/v1.5.0-beta-3/kotlin/kotlin.bzl

As of Bazel 4, protoc and most tools are dependend on via the exec
configuration rather than the host configuration. By also using the exec
transition in grpc_kotlin, unnecessary (and very costly) rebuilds of
protoc can be prevented.

* to compose

* bump compose and cleanup

* move service out of composable

* cleanup

* rename GreeterService

* better resource mgmt - maybe

* bump android versions

* examples only on jdk 1.11

* try new setup-java

* prepare for 1.2.1

* only sign if there is a gpg key