Add more precise instructions

Author: alexeyzab

.github/issue_template.md

@@ -2,7 +2,7 @@ Checklist for adding a package:
 - [ ] specified the Stackage LTS version in the summary
 - [ ] On your own machine, in a new directory, you have succesfully run the following set of commands (replace `$package` with the name of the package that is submitted, `$version` is the version of the package you want to get into the LTS series, and `$lts` is the desired LTS series):
 
-      stack unpack $package
+      stack unpack $package-$version
       cd $package-$version
       stack init --resolver lts-$lts
       stack build --haddock --test --bench --no-run-benchmarks