Adding personnal template for tag pages setting

Hi Dan,

Here is the pull request to answer issue https://github.com/DanReeves/picotags/issues/11

I've tested it on my localhost and it works like a charm, just like in the Pico Leaflet plugin I've written.

I'll open a new issue concerning the exclude feature and something I've mentionned in one my posts of my last (big) pull request.

See you.