Add README w/ install info

[djfarrelly]

Purpose

To make it easier to get started with this tool 😄

What it could look like:

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kubesecret

A tool to manage secrets in kubernetes

Installation

Run t

VERSION="0.3"
curl -L https://github.com/bufferapp/kubesecret/releases/download/$VERSION/kubesecret-`uname -s` > /usr/local/bin/kubesecret
chmod +x /usr/local/bin/kubesecret

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Notes

• We currently make the binary lowercase so to use uname -s we could make the binary -Linux-...
• Can we drop the amd64 part of the binary file name for brevity?
• We could also add some basic usage of the tool on the readme as well 👍

[kiriappeee]

Hey @djfarrelly, all these make sense. Shall make the changes. Thanks for the nudge here