add a SPDX compliant license and organization into the published mps-extensions pom

[KemalSoysal]

When checking for license policy constraints, the missing license information in the pom requires manual adjustment to the checking.

The pom.xml is described for the license aspect and recommends to use the SPDX identifiers.

The SPDX catalog states for the Apache 2.0 License the identifier Apache-2.0.

Add a license notice in the pom by creating the appropriate tags in the pom.xml

<project ...
...
  <licenses>
    <license>
      <name>Apache-2.0</name>
      <url>http://www.apache.org/licenses/LICENSE-2.0.txt</url>
      <distribution>repo</distribution>
      <comments>A business-friendly OSS license</comments>
    </license>
  </licenses>
...
</project>

Additionally Apache 2.0 requires the copyright notice. For this it could be enough to add the organization tag to the pom.xml

  <organization>
    <name>JetBrains s.r.o.</name>
    <url>https://www.jetbrains.com</url>
  </organization>

No source files are needed with Apache 2.0.