`boot run` not working out of the box for lack of `env`

Nobody has claimed this yet.

It seems there's a problem with the template when used with the `+boot` flag. When I type `boot run` I get the following error:
```
java.io.FileNotFoundException: Could not locate lumboot/env__init.class, lumboot/env.clj or lumboot/env.cljc on classpath.
clojure.lang.ExceptionInfo: Could not locate lumboot/env__init.class, lumboot/env.clj or lumboot/env.cljc on classpath.
```
AFAICT this is because none of the the env-directories are added to the classpath. I've gotten it to to work by prepending the following to the body of the `run` task:
```
(merge-env! :source-paths #{"env/prod/clj"}
:resource-paths #{"env/prod/resources"})
```
Since I'm fairly new to Luminus I'm unsure if this is the correct solution. Maybe this is not even a bug, in which case instructions as to how the `run` task should be used would be helpful.

Start with the +boot template and its run task, then reproduce the reported `boot run` failure and inspect how the env/prod/clj and env/prod/resources paths are assembled. Determine whether the template should include those paths or document a different invocation; done means the intended out-of-the-box behavior is verified or clearly documented.

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