add default_config verb to create a default configuration file

[ottojo]

Information about the config file format is hard to find, i think this makes it easier to use.

This adds a verb default_config which just writes the default config file already present in the code to a file, to be customized by the package author.

[mikeferguson]

I just tried this out (rebased on top of main) and I do think it would be a helpful addition to this tool (everything worked as advertised)

[Yadunund]

@ottojo thanks for the contribution and thank you @mikeferguson for reviewing this PR.

Left a couple of nitpicks to address before we can merge.

Alternatively @mikeferguson if you could open a PR with the main rebase and the copyright headers added, happy to merge that in as long as the origin commit authored by @ottojo is preserved.

[Yadunund]

Add copyright header

[ottojo]

I added a header, not sure if it is expected to dedicate copyright to OSRF, that can be done if desired.

[Yadunund]

Add copyright header.

[ottojo]

Nice to see some activity here, I think package documentation is such an important aspect of ROS with much room for improvement!

I rebased the commit to latest main, and tested it myself as well.

[tfoote]

Thanks for pushing this forward

[Yadunund]

Looks like our linters have flagged some formatting issues with the changes proposed. Do you mind addressing them?

[ottojo]

should be fixed! @Yadunund