* feat(precheck): check if power pins have `USE` in definition
* fix: expect zero or more spaces, instead of one or more
* feat(precheck): check for missing `USE POWER`
* feat(precheck): check for missing `USE GROUND`
* feat(precheck): add simple README with link to LEF/DEF reference manual
Switching from `gfm` to `markdown` should enable more formatting options. The extensions have been configured to be similar to `gfm` but provide some additional things, like `line_blocks` and `lists_without_preceding_blankline`s.
This was caused by creating a page before first checking whether there was any content for that page beforehand, so it would result in a rogue white page with no content.
kris j