Add JohnAlbin to MAINTAINERS.txt

So I was discussed a few times in #621618: Revamp MAINTAINERS.txt, but the changes went in without me ever being aware of that ticket. :-)

Being the Stark maintainer is probably appropriate. However, that means I'm the maintainer of 35 lines of CSS that was designed to be completely inconsequential and throw-away. “This layout method works reasonably well, but shouldn't be used on a production site because it can break.” ha! yay, me.

Talked to webchick in IRC about a couple question marks (literal “?”s) in the MAINTAINERS.txt and she said:

It helps to have an established track record for doing the work too before asking for inclusion.
[…]
But the bar is pretty low. "John Albin" is certainly better than "?" even if you only looked at the queue once in awhile.
But ostensibly what we're saying there is "If you have a patch you want to run past someone about block module, talk to this guy."

I'd like to additionally be put under the Theme system, block module, and… *sigh*… the Garland theme.

My work on the Theme system is pretty obvious.

I volunteer to be under Garland because I'm very familiar with the code and I doubt anyone else will ever volunteer for it. I've already got my name on Pushbutton, Chameleon and Bluemarine, so why not.

For the block module, most of the work I've done has been on the contrib side, trying to correct API limitations of the block module. I've done a couple minor patches for block module in D7. Mostly, I'm willing to maintain the code with an eye for incorporating my block API tweaks into D8. If anyone else has done more d7 block work and volunteers to maintain block.module, I'm happy to have them replace my name with theirs; I'll just work to get it back for D8. :-)