STYLE: Improve the first interaction message style
STYLE: Improve the first interaction message style

Improve the first interaction message style:
- Remove the section header markup (`#`) and avoid an excessively large
  font/avoid making the interaction message prevail over the issue/PR
  text itself.
- Use the YAML literal block style syntax (`|`) and remove the newline
  explicit markup.

richardbeare/ITK,Kitware/ITK,hjmjohnson/ITK,richardbeare/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,Kitware/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,richardbeare/ITK,Kitware/ITK,richardbeare/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,Kitware/ITK,Kitware/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,Kitware/ITK,hjmjohnson/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,hjmjohnson/ITK,Kitware/ITK,BRAINSia/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK