ci: Add issue and PR assigner

Adds actions that will automatically assign users to reviews
and issues

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
diff --git a/.github/workflows/issue.yml b/.github/workflows/issue.yml
new file mode 100644
index 0000000..65bf5c4
--- /dev/null
+++ b/.github/workflows/issue.yml
@@ -0,0 +1,19 @@
+name: Issue assignment
+
+on:
+  issues:
+    types: [opened]
+
+jobs:
+  auto-assign:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+    if: github.repository == 'mcu-tools/mcuboot'
+    steps:
+      - name: 'Auto-assign issue'
+        uses: pozil/auto-assign-issue@v2
+        with:
+          repo-token: ${{ secrets.USER_TOKEN }}
+          assignees: d3zd3z, nordicjm, de-nordic, davidvincze
+          allowSelfAssign: true
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
new file mode 100644
index 0000000..b0f363a
--- /dev/null
+++ b/.github/workflows/pr.yml
@@ -0,0 +1,18 @@
+name: PR assignment
+
+on:
+  pull_request:
+    types: [opened, edited, synchronize, reopened]
+
+jobs:
+  auto-assign:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+    if: github.repository == 'mcu-tools/mcuboot'
+    steps:
+      - uses: actions/checkout@v1
+      - uses: ohnogumi/auto-reviewers@v0.0.5
+        with:
+          token: ${{ secrets.USER_TOKEN }}
+          config: CODEOWNERS