Add web-ext-lint job

Change-Id: I12018ea457599ba0dd611c05464f3c1dd14d0fba
diff --git a/roles/web-ext-lint/defaults/main.yaml b/roles/web-ext-lint/defaults/main.yaml
new file mode 100644
index 0000000..5dc93b5
--- /dev/null
+++ b/roles/web-ext-lint/defaults/main.yaml
@@ -0,0 +1,3 @@
+---
+source_dir: src
+extra_lint_flags:
diff --git a/roles/web-ext-lint/tasks/main.yaml b/roles/web-ext-lint/tasks/main.yaml
new file mode 100644
index 0000000..62cf135
--- /dev/null
+++ b/roles/web-ext-lint/tasks/main.yaml
@@ -0,0 +1,7 @@
+- name: Run the web-ext linter
+  shell:
+    cmd: >-
+      web-ext lint --no-input --boring
+      {{ '--source-dir=' + source_dir if source_dir else '' }}
+      {{ extra_lint_flags }}
+    chdir: "{{ zuul.project.src_dir }}"