stlink: added 1.0.0 release

This is to add a new formula `stlink`, previously attempted at #14175 by @henryeherman two years back. Build system has then changed to autoconf/automake, and now it comes with a (relatively) stable tag back in February.

First attempt in making a brew - please advise if anything's wrong here. Thanks.
Can this test be modified to do something more substantial than e.g. `--version` or `--help`? See `cmake.rb` for an example of an application formula with a good test and `tinyxml2.rb` for an example of a library formula with a good test. Thanks!