internal/e2e: rename existing testscript and add a summary

We will soon add more end-to-end test scripts,
so one of them being called "basic" is not very helpful anymore.
It's also helpful if the script begins with a short summary
describing what the test is meant to do.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: Ic464983b0e503c4c08d5d3f49984dcc20ab82b65
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1171909
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>

Author: mvdan

internal/e2e/testdata/script/basic.txtar internal/e2e/testdata/script/github_app_public.txtar

@@ -1,3 +1,8 @@
+# Create a public GitHub repository in an org with the GitHub App
+# "CUE Module Publisher" installed for all repositories.
+# Push a git tag with a simple CUE module, wait for the app to publish the version,
+# and then fetch the module as a dependency via cmd/cue.
+
 create-github-repo
 env VERSION=v0.0.1
 env MODVER=${MODULE}@v0