Add tests for nginx.conf directives (#1)

Adds tests to make sure all the `nginx.conf` directives (the redirects and rewrites and such) are all correct.

- Uses the `busted` framework
- The tests are run in a Docker container by the bash script `test.sh`
- Self-signed certs are generated in `Dockerfile` for all the domain names
- Adds new `Makefile` commands: `test`, `image-build` and `image-rm`

Reviewed-on: #1
Co-authored-by: Catalin Mititiuc <webdevcat@proton.me>
Co-committed-by: Catalin Mititiuc <webdevcat@proton.me>

spec/unixstreamsrvr.moon

@@ -0,0 +1,14 @@
+-- modified from
+-- https://github.com/lunarmodules/luasocket/blob/4844a48fbf76b0400fd7b7e4d15d244484019df1/test/unixstreamsrvr.lua
+socket = require "socket"
+socket.unix = require "socket.unix"
+u = assert socket.unix.stream!
+assert u\bind "/run/gitea/gitea.socket"
+assert u\listen!
+assert u\settimeout 1
+c = assert u\accept!
+
+while true
+  m = assert c\receive!
+  break if m == ""
+  print m