Add GitHub Actions CI.

[junaruga]

Hi, I created a PR to enable GitHub Actions CI for this repository. The CI log on my forked repository is here.

For the libraries to build bundled htslib, I referred to the Debian package recipe file. https://salsa.debian.org/med-team/htslib/-/blob/master/debian/control

I checked the CI on my forked repository. https://github.com/junaruga/FASTK/actions/runs/2981840619

The ubuntu-latest means Ubuntu 20.04.4 right now.

Examples

Here are some cases in other projects.

• hifiasm: https://github.com/chhylp123/hifiasm/blob/master/.github/workflows/ci.yaml
• minimap2: https://github.com/lh3/minimap2/blob/master/.github/workflows/ci.yaml
• bowtie2: https://github.com/BenLangmead/bowtie2/tree/master/.github/workflows
• ruby: https://github.com/ruby/ruby/tree/master/.github/workflows