Fix options pane location + update to 1.5.1

[thebluepotato]

The (very) recent release of 1.5.0 moved the options pane XHTML inside the content folder. As this is cleaner, I changed the code to reflect it. Also a good opportunity to test if updates to 1.5.1 will work! Fixes #43

[thebluepotato]

@bwiernik Sorry for the hassle

[bwiernik]

No problem -- I don't have a build script for the .xpi set up on my current machine -- could you make one and post it here?

[thebluepotato]

No problem -- I don't have a build script for the .xpi set up on my current machine -- could you make one and post it here?

I've been updating the BAT script throughout the PR, but I don't have Windows. What's your platform? Would GitHub actions be easier to use? I guess that would allow automation of version numbers across the manifests.

[bwiernik]

I'm working on a Mac at this point

[thebluepotato]

Ok so do I, I'll draft something over the weekend. In the meantime, if you want to release 1.5.1, you can do the same as you did for .0, namely zip all folders, js files, the JSON manifest, install.rdf and chrome.manifest. I've moved options.xhtml so now it should indeed stay in the content folder.