add basic man page - fixes #17

[01micko]

This can be added to later as it just has the basics.

[johanmalm]

Thanks. Good idea.
I'd prefer the man page in .scd format like we've done in labwc itself.
Fancy doing the conversion?

[01micko]

Sure. Just have to add scdoc build time dependency. I did consider that but thought the extra dep may have been unwanted.
Do you have anything to add @johanmalm to the page?
Won't be until this evening AEST time.

[01micko]

Had to recall a bit of meson fu :)

Should be ready for merge.

[johanmalm]

Thanks. Great effort.
Can expand on content later.

[01micko]

Thanks :)