Setup CLA workflow; run CI for PRs (#408)

Author: rmeissner

.github/workflows/ci.yml

@@ -1,5 +1,5 @@
 name: safe-contracts
-on: [push]
+on: [ push, pull_request ]
 
 jobs:
   tests:

.github/workflows/cla.yml

@@ -0,0 +1,36 @@
+name: "CLA Assistant"
+on:
+  issue_comment:
+    types: [ created ]
+  pull_request_target:
+    types: [ opened, closed, synchronize ]
+
+jobs:
+  CLAssistant:
+    runs-on: ubuntu-latest
+    steps:
+      - name: "CLA Assistant"
+        if: (github.event.comment.body == 'recheck' || github.event.comment.body == 'I have read the CLA Document and I hereby sign the CLA') || github.event_name == 'pull_request_target'
+        # Beta Release
+        uses: cla-assistant/github-action@v2.1.3-beta
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          # the below token should have repo scope and must be manually added by you in the repository's secret
+          PERSONAL_ACCESS_TOKEN: ${{ secrets.PERSONAL_ACCESS_TOKEN }}
+        with:
+          path-to-signatures: 'signatures/version1/cla.json'
+          path-to-document: 'https://safe.global/cla/'
+          # branch should not be protected
+          branch: 'cla-signatures'
+          allowlist: rmeissner,Uxio0,*bot # may need to update this expression if we add new bots
+
+          #below are the optional inputs - If the optional inputs are not given, then default values will be taken
+          #remote-organization-name: enter the remote organization name where the signatures should be stored (Default is storing the signatures in the same repository)
+          #remote-repository-name:  enter the  remote repository name where the signatures should be stored (Default is storing the signatures in the same repository)
+          #create-file-commit-message: 'For example: Creating file for storing CLA Signatures'
+          #signed-commit-message: 'For example: $contributorName has signed the CLA in #$pullRequestNo'
+          #custom-notsigned-prcomment: 'pull request comment with Introductory message to ask new contributors to sign'
+          #custom-pr-sign-comment: 'The signature to be committed in order to sign the CLA'
+          #custom-allsigned-prcomment: 'pull request comment when all contributors has signed, defaults to **CLA Assistant Lite bot** All Contributors have signed the CLA.'
+          #lock-pullrequest-aftermerge: false - if you don't want this bot to automatically lock the pull request after merging (default - true)
+          #use-dco-flag: true - If you are using DCO instead of CLA