Declare module descriptor (JPMS, Java 9+, Project Jigsaw)

[C-Otto]

Using spring-shell in a project which uses JPMS (Project Jigsaw) produces errors like this:

package org.springframework.shell.standard is declared in the unnamed module

Please provide a module name for the library.

$ jar --file=~/.gradle/caches/modules-2/files-2.1/org.springframework.shell/spring-shell-core/2.0.0.RELEASE/75a94aaa62302ee0d5020fca1962b5d63c23a075/spring-shell-core-2.0.0.RELEASE.jar --describe-module
No module descriptor found. Derived automatic module.

[email protected] automatic
requires java.base mandated
contains org.springframework.shell
contains org.springframework.shell.jline
contains org.springframework.shell.result

[jvalkeal]

Closing this for limited support #529.

We can revisit if ecosystem gets better. More info i.e. in spring-projects/spring-framework#18079 and spring-projects/spring-boot#13799.