Install deps *before* tests in Actions workflow

While creating the `$ npm install` step in the
GitHub Actions workflow, I forgot to state the fact that
the `$ npm test` step "needs" the install deps step
to have successfully run first.

.github/main.workflow

@@ -1,5 +1,5 @@
 workflow "Verify changes on push" {
-  resolves = ["Run all tests"]
+  resolves = ["Run unit tests"]
   on = "push"
 }
 
@@ -8,7 +8,8 @@ action "Install dependencies" {
   args = "install"
 }
 
-action "Run all tests" {
+action "Run unit tests" {
   uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = "Install dependencies"
   args = "test"
 }