Default ts_ignore suggestions

[mm12]

The current default .ts_ignore (found in .ts_ignore_template) is lacking. If you think a particular filetype should be ignored by default (or shouldn't), please toss it in here.

Example discussion around the `json` file extension:

We exclude `xmp` and `aae` (which are made for image metadata), but also `json` (which might contain image metadata, or might not). I presume `json` might be for legacy reasons, though I don't see why it couldn't use a tighter filename pattern in that case. If not, why is it different from `csv`, `yaml`, `xml`, `tsv`, etc?

Even if these items aren't added to the default list, hopefully users will find it useful to reference for their own .ts_ignores!

[mm12]

Partial downloads can currently be discovered by default. Once the browser decides the download has succeeded/failed, the file will be renamed and it will become unlinked. In addition, future efforts (see #36) will make this worse, as the file won't have a consistent checksum until it is completed.

Known download file extensions:

*.part
*.crdownload
*.download
*.opdownload
*.tmp
*.temp