add example configuration for vs code

[casartar]

I often use vs code with cortex debug. But could not find instructions on how to use tigard with cortex debug. So I thought a little help in the manual would be useful.

[securelyfitz]

Pardon my delay in taking a look at this. Thanks for figuring it out - however, i'm pondering if the readme is the best place for this since as it is, it requires the combination of tigard + openocd + visualstudio + stm32f091. The he tigard documentation is already a big flat readme, I'm hesitant to add things that aren't going to be relevant to a large portion of users. This might be better suited to the openocd or visualstudio documentation, because it's really about getting openocd and visualstudio working and the tigard.cfg file is the only thing tigard-specific.

However, I could add note in the readme pointing to this PR for people using visualstudio.

[securelyfitz]

Rather than make the readme longer, e2aa342 added a link to this PR in the readme so folks can learn more if they want to setup VS Code