documentation - README.adoc

[hks1]

documentation needs to be improved
e.g. in https://github.com/spring-guides/gs-spring-boot-docker#containerize-it
"It is then copied (by the COPY command) the project JAR file into the container as app.jar" is to be re-written as
"It then copies (by the COPY command) the project JAR file into the container as app.jar"