Don't use substripts in HTML if there is just a number in the
subscript: "R1", not "R<sub>1</sub>", except for characteristic
impedance. And of course still use "Z<sub>in</sub>", not "Zin".
This is also consistent with the images.
- replace "⋅" not displayed on Windows (for some reason) by "·"
- replace the double space at end of lines by the tag <br>
A translatable string cannot ends by 2 spaces, because they are not really visible
The previous converter (maddy) is still available, during some time.
We therefore have the time to choose between them.
sundown is better to convert a md text, but is written to C
maddy has a few issues to convert a md text, but is written to C++
Both have no dependency.