[UNOMI-592] - a tip for building on non-English Windows env

[woonsan]

A tip in manual for non-English Windows users to avoid a build error due to the asciidoc-maven-plugin error.
Building on a non-English Windows machine, it is very likely to see a build error due to an encoding issue like the following example:

[ERROR] Failed to execute goal org.asciidoctor:asciidoctor-maven-plugin:1.6.0:process-asciidoc (output-html) on project unomi-manual: Execution output-html of goal org.asciidoctor:asciidoctor-maven-plugin:1.6.0:process-asciidoc failed: unknown encoding name - MS949 -> [Help 1]

---

• Make sure there is a JIRA issue filed
  for the change (usually before you start working on it). Trivial changes like typos do not
  require a JIRA issue. Your pull request should address just this issue, without pulling in other changes.
• Format the pull request title like [UNOMI-XXX] - Title of the pull request
• Provide integration tests for your changes, especially if you are changing the behavior of existing code or adding
  significant new parts of code.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
  Copy the description to the related JIRA issue
• Run mvn clean install -P integration-tests to make sure basic checks pass. A more thorough check will be
  performed on your pull request automatically.

To make clear that you license your contribution under the Apache License Version 2.0, January 2004
you have to acknowledge this by using the following check-box.

• I hereby declare this contribution to be licenced under the Apache License Version 2.0, January 2004

[jkevan]

Hello Woosan,

Thanks a lot for the PR.

Regards,
Kevan