Request reviews from per1234 when maintainer attention is needed

Previously, the submission system was configured to automatically request reviews from the `arduino/team_tooling` team.
This doesn't work, likely due to the access token provided by GitHub not having the necessary permissions. However,
requesting from individual users works fine and in the end bothering the whole Tooling Team is probably a bad idea.

.github/workflows/manage-prs.yml

@@ -2,6 +2,9 @@ name: Manage PRs
 
 env:
   SUBMISSION_PARSER_VERSION: 1.0.0-rc6 # See: https://github.com/arduino/library-manager-submission-parser/releases
+  MAINTAINERS: |
+    # GitHub user names to request reviews from in cases where PRs can't be managed automatically.
+    - per1234
 
 on:
   # pull_request_target trigger is used instead of pull_request so the token will have the write permissions needed to
@@ -410,8 +413,7 @@ jobs:
           owner: ${{ github.repository_owner }}
           repo: ${{ github.event.repository.name }}
           pull_number: ${{ github.event.pull_request.number }}${{ github.event.issue.number }}
-          team_reviewers: |
-            - arduino/team_tooling
+          reviewers: ${{ env.MAINTAINERS }}
 
   not-submission:
     needs:
@@ -429,8 +431,7 @@ jobs:
           owner: ${{ github.repository_owner }}
           repo: ${{ github.event.repository.name }}
           pull_number: ${{ github.event.pull_request.number }}${{ github.event.issue.number }}
-          team_reviewers: |
-            - arduino/team_tooling
+          reviewers: ${{ env.MAINTAINERS }}
 
       - name: Comment on required review
         uses: octokit/request-action@v2.x
@@ -479,8 +480,7 @@ jobs:
           owner: ${{ github.repository_owner }}
           repo: ${{ github.event.repository.name }}
           pull_number: ${{ github.event.pull_request.number }}${{ github.event.issue.number }}
-          team_reviewers: |
-            - arduino/team_tooling
+          reviewers: ${{ env.MAINTAINERS }}
 
       - name: Comment on unexpected failure
         uses: octokit/request-action@v2.x