Enable support for multi-arch container images: arm, arm64 and amd64.

Add Container Build documentation.

docs/Container Build.md

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+
+# Container Build
+> **WARNING:** As a user of Reloader there is no need to build containers, these are freely available here: https://hub.docker.com/r/stakater/reloader/
+
+Multi-architecture approach is based on original work by @mdh02038: https://github.com/mdh02038/Reloader
+
+Images tested on linux/arm, linux/arm64 and linux/amd64.
+
+# Install Pre-Reqs
+The build environment requires the following packages (tested on Ubuntu 20.04):
+* golang
+* make
+* qemu (for arm, arm64 etc. emulation)
+* binfmt-support
+* Docker engine
+
+## Docker
+Follow instructions here: https://docs.docker.com/engine/install/ubuntu/#install-using-the-repository
+
+Once installed, enable the experimental CLI:
+```
+export DOCKER_CLI_EXPERIMENTAL=enabled
+```
+Login, to enable publishing of packages:
+```
+sudo docker login
+```
+## Remaining Pre-Reqs
+Remaining Pre-Reqs can be installed via:
+```
+sudo apt install golang make qemu-user-static binfmt-support -y
+```
+
+# Publish Multi-Architecture Image
+To build/ publish multi-arch Docker images clone repository and execute from repository root:
+```
+sudo make release-all
+```
+
+# Additional Links/ Info
+* *https://medium.com/@artur.klauser/building-multi-architecture-docker-images-with-buildx-27d80f7e2408