make more distinction between Yes and N/A in the readme table

[prusnak]

... by using checkmark ✓ and cross ✗

The original formatting was making the table quite hard to grasp as there were so many letters present on screen at once.

This is how the rendered readme looks like: https://github.com/prusnak/HWI/tree/readme-table#device-support

We might even consider using ❌ and ✅ emojis, but these might not be as widely supported (they are in the Unicode 6.0 standard from 2010). The characters I used are part of Unicode 1.1 from 1993.

[achow101]

The table actual shows a tri-state. Yes means "supported by firmware and implemented in HWI". No means "supported by firmware and not implemented by HWI" (we don't have any on this table AFAICT). N/A means "not supported by the firmware". So just ✓ and ✗ is not sufficient.

A previous PR which implemented something similar was closed because of concerns with how this would be displayed in text editors, although I think that used Github's emojis rather than unicode. I think most terminals and text editors support unicode so this probably isn't an issue, especially with characters that are part of a very old unicode version.

[prusnak]

Right. There is no "No" in the table at the moment (good job!).

I updated the PR to include the legend and replaced cross with dash for N/A.

[achow101]

ACK 40c6887