Add deploy workflow (#18)

* Add publish workflow

* Formatting

Author: matthewelwell

.github/workflows/publish.yml

@@ -0,0 +1,16 @@
+on:
+  push:
+    tags:
+      - "*"
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out
+        uses: actions/checkout@v2
+
+      - name: Publish package to hex.pm
+        uses: wesleimp/action-publish-hex@v1
+        env:
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}

.gitignore

@@ -27,3 +27,6 @@ flagsmith_engine-*.tar
 
 # Ignore the dialyzer PLTS
 /priv/plts
+
+.direnv
+.tool-versions