all: add minimal GoReleaser configuration for nightly builds

This is step one of many towards automated nightly releases.

This gets us downloadable binaries, which can be grabbed manually
from GitHub Releases...in theory, since this is untested,
because GitHub Actions.

Once this is working, future steps include:

- documentation
- homebrew support (and other package managers?)
- auto-updates
- installers
- blah blah blah

diff --git a/.gitignore b/.gitignore
index 78d8a86..76fce36 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,6 @@
 
 # Local environment variables
 .envrc
+
+# goreleaser builds
+dist