Add gitpod config

this commit adds support for Gitpod.io, a free automated
dev environment that makes contributing and generally working on GitHub
projects much easier. It allows anyone to start a ready-to-code dev
environment for any branch, issue and pull request with a single click.

.gitpod.Dockerfile

@@ -0,0 +1,13 @@
+FROM gitpod/workspace-full-vnc
+
+USER gitpod
+
+# Install custom tools, runtime, etc. using apt-get
+# For example, the command below would install "bastet" - a command line tetris clone:
+#
+# RUN sudo apt-get -q update && #     sudo apt-get install -yq bastet && #     sudo rm -rf /var/lib/apt/lists/*
+#
+# More information: https://www.gitpod.io/docs/config-docker/
+
+RUN bash -c ". /home/gitpod/.sdkman/bin/sdkman-init.sh \
+             && sdk install jbang"

.gitpod.yml

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+tasks:
+  - init: ./gradlew build
+image:
+  file: .gitpod.Dockerfile

readme.adoc

@@ -1,11 +1,13 @@
+
 = j'bang - Having fun with Java scripting
 :toc:
 :toc-placement:
 :icons: font
 
 image:https://img.shields.io/github/release/maxandersen/jbang.svg[Release,link=https://github.com/maxandersen/jbang/releases]
 image:https://github.com/maxandersen/jbang/workflows/ci-build/badge.svg[Build Status,link=https://github.com/maxandersen/jbang/actions]
-image:https://che.openshift.io/factory/resources/factory-contribute.svg[Contribute, link=https://che.openshift.io/f?url=https://github.com/maxandersen/jbang]
+image:https://che.openshift.io/factory/resources/factory-contribute.svg[Che, link=https://che.openshift.io/f?url=https://github.com/maxandersen/jbang]
+image:https://img.shields.io/badge/Gitpod-Workspace-blue?logo=gitpodp[Gitpod, link=https://gitpod.io/#https://github.com/maxandersen/jbang] 
 
 
 == Intro