chore: set up commitlint, husky, and prettier (#1451)

* chore: add prettier configuration

Signed-off-by: Xe Iaso <me@xeiaso.net>

* format: run prettier tree-wide

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(prettier): ignore intentionally ungrammatical files

Signed-off-by: Xe Iaso <me@xeiaso.net>

* ci: add PR title lint rule

Signed-off-by: Xe Iaso <me@xeiaso.net>

* ci: add DCO check

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: add commitlint and husky

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: add CONTRIBUTING guidelines

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: set SKIP_INTEGRATION in precommit tests

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: update spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* ci(dco): remove reopened trigger

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: remove dead file

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore(prettier): don't format nginx includes

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/config/testdata/bad/regex_ends_newline.yaml

@@ -1,17 +1,17 @@
 bots:
-- name: user-agent-ends-newline
-  # Subtle bug: this ends with a newline
-  user_agent_regex: >
-    Mozilla
-  action: CHALLENGE
-- name: path-ends-newline
-  # Subtle bug: this ends with a newline
-  path_regex: >
-    ^/evil/.*$
-  action: CHALLENGE
-- name: headers-ends-newline
-  # Subtle bug: this ends with a newline
-  headers_regex:
-    CF-Worker: >
-      .*
-  action: CHALLENGE
+  - name: user-agent-ends-newline
+    # Subtle bug: this ends with a newline
+    user_agent_regex: >
+      Mozilla
+    action: CHALLENGE
+  - name: path-ends-newline
+    # Subtle bug: this ends with a newline
+    path_regex: >
+      ^/evil/.*$
+    action: CHALLENGE
+  - name: headers-ends-newline
+    # Subtle bug: this ends with a newline
+    headers_regex:
+      CF-Worker: >
+        .*
+    action: CHALLENGE