feat: Add templating mechanism with Asciidoc alternative

[dvaillant]

fix issue #12

[adoble]

I have been putting some thought into how templates should be handled (and what is meant with template). Currently the template is hard coded to use the Nygard lightweight ADR template in English. I have been working on a means of specifying a template file (during the initialization) that can be modified by the tool with the ADR name, date etc. (i.e. the Record fields). As such a user can write their own template using:

• whatever structure they want to use. For instance, there is some interest in also supporting the MADR structure and organizations may have their own structures.
• in whatever language they want to use (e.g. German, French, English, ..)
• in whatever document format they want (e.g. Markdown, Asciidoc, …)

So, for instance a user command could be:

adr init -t ~/templates/madr_template.md

with the template being written in markdown, or

adr init -t ~/dev_templates/my-org-template.txt

with the template being written in asciidoc.

As the command line processing is getting more complicated, I’ve taken some time to refactor the tool to use the Picocli framework (picocli.info). The next step is to develop the general templating mechanism.

As you can see, I’m trying to move away from the hardcoded ADRs to a more flexible option and the PR doesn’t move the tool towards that

[adoble]

This functionality has now been implemented in release v3.0