chore: add auto-approve bot (#1320)

Adds an [auto approve configuration](https://github.com/googleapis/repo-automation-bots/blob/master/packages/auto-approve/README.md) to automatically approve the PRs that update discovery artifacts.

Only PRs that match these conditions will be approved:
- PR Author is `yoshi-code-bot`
- PR Title is `chore: Update discovery artifacts`
- Files changed limited to the following
`docs/dyn/index.md` , `docs/dyn/*.html"` or `googleapiclient/discovery_cache/documents/*.json`

Author: parthea

.github/CODEOWNERS

@@ -8,4 +8,6 @@
 *               @googleapis/yoshi-python
 
 # The python-samples-reviewers team is the default owner for samples changes
-/samples/  @googleapis/python-samples-owners
+/samples/  @googleapis/python-samples-owners
+
+.github/auto-approve.yml @googleapis/github-automation @googleapis/yoshi-python

.github/auto-approve.yml

@@ -0,0 +1,20 @@
+# https://github.com/googleapis/repo-automation-bots/tree/master/packages/auto-approve
+
+rules:
+
+# incoming PRs from yoshi-code-bot
+- author: "yoshi-code-bot"
+
+# Title for PRs from yoshi-code-bot MUST start with `chore: Update discovery artifacts`.
+# Title must be regex.
+  title: "^chore: Update discovery artifacts"
+
+# The only changed file paths in an incoming PR MUST be exactly
+# `"^docs/dyn/index.md$"` or follow either one of these patterns `"docs/dyn/*.html"`
+# or `"googleapiclient/discovery_cache/documents/*.json"` . These are
+# listed in regex. If this property is omitted, auto-approve bot will allow PRs
+# that match the author and title to merge, without checking the file paths.
+  changedFiles:
+  - "^docs/dyn/index.md$"
+  - "^docs/dyn/.*\\.html$"
+  - "^googleapiclient/discovery_cache/documents/.*\\.json$"