Add ability to search proposals by title and body

[nodunayo]

Sometimes looking at a list of speaker's names, proposal titles, or events isn't quite what you need. Sometimes, you want to search for a keyword or two and see what's out there. For those people, I propose that we add the ability to search proposals by their title and body.

Also, as the database grows (hopefully!) search will be even more useful.

[andrew]

@nodunayo you should add the "help wanted" label ;)

[nodunayo]

@andrew I guess you're right! Whenever I make issues I always assume the default is "help wanted" — that's why I made the issue. But, yes — I'll add it! :-)

[nodunayo]

@esmale Thanks, David! :-D