Adding support for strikethrough and checkboxes

We get asked about support for strikethrough and checkboxes frequently. Here are our thoughts on that:

1) Tot is based on plain text with standard Markdown for a limited amount of styling. Strikethrough is not a part of the original Markdown specification and current extensions implement it in different ways (sometimes one tilde, sometimes two, sometimes a library compile-time option, etc.) If the Markdown specification changes to incorporate strikethrough, we'll happily adopt it, but our guess is that's unlikely to happen.

2) Similarly, checkboxes are non-standard Markdown (Github task lists). We have some ideas to explore there, but anything we do will be based on working with plain text and have a good interaction on iOS (where tap targets are typically much larger than the surrounding text).

3) Tot works best as a temporary storage area. When you're finished with a task, just delete it :-)