Update developer docs (#851)

Problems:
- Go style guide is missing guideline on inline error checking
- Pull request guide is missing guideline on PR titles

Solution: Add guidelines to relevant docs

Author: kate-osborn

docs/developer/go-style-guide.md

@@ -200,6 +200,27 @@ func (int required, ...Options) {
 
 ## Error Handling
 
+### Prefer inline error handling
+
+When possible, use inline error handling.
+
+DO:
+
+```go
+if err := execute(); err != nil {
+    // handle error
+}
+```
+
+DO NOT:
+
+```go
+err := execute()
+if err != nil {
+    // handle error
+}
+```
+
 ### Do not filter context when returning errors
 
 Preserve error context by wrapping errors as the stack unwinds. Utilize native error wrapping with `fmt.Errorf` and

docs/developer/pull-request.md

@@ -2,7 +2,10 @@
 
 ## Submitter Guidelines
 
-- Fill in [our pull request template](/.github/PULL_REQUEST_TEMPLATE.md). 
+- Title the PR using customer-focused language. The release notes are generated from PR titles, so the titles should
+  describe the feature from the user's perspective and avoid implementation details. For example, instead of "Add debug
+  boolean", write "Support configurable debug mode".
+- Fill in [our pull request template](/.github/PULL_REQUEST_TEMPLATE.md).
 - Make sure to include the issue number in the PR description to automatically close the issue when the PR mergers.
   See [Closing Issues via Pull Requests](https://github.blog/2013-05-14-closing-issues-via-pull-requests/) for details.
 - For significant changes, break your changes into a logical series of smaller commits. By approaching the changes