add readme file to replace missing config file comments

Author: mowies

.chloggen/README.md

@@ -0,0 +1,34 @@
+### Changelog folder
+
+This repo uses `chloggen` to manage its changelog files. You can find the source code for the tool [here](https://github.com/open-telemetry/opentelemetry-go-build-tools/tree/main/chloggen).
+
+Here is a quick explanation of the `config.yaml` file for chloggen:
+
+```yaml
+# The directory that stores individual changelog entries.
+# Each entry is stored in a dedicated yaml file.
+# - 'chloggen new' will copy the 'template_yaml' to this directory as a new entry file.
+# - 'chloggen validate' will validate that all entry files are valid.
+# - 'chloggen update' will read and delete all entry files in this directory, and update 'changelog_md'.
+# Specify as relative path from root of repo.
+# (Optional) Default: .chloggen
+entries_dir: .chloggen
+
+# This file is used as the input for individual changelog entries.
+# Specify as relative path from root of repo.
+# (Optional) Default: .chloggen/TEMPLATE.yaml
+template_yaml: .chloggen/TEMPLATE.yaml
+
+summary_template: .chloggen/summary.tmpl
+
+# The CHANGELOG file or files to which 'chloggen update' will write new entries
+# (Optional) Default filename: CHANGELOG.md
+change_logs:
+  user: CHANGELOG.md
+  api: CHANGELOG-API.md
+
+# The default change_log or change_logs to which an entry should be added.
+# If 'change_logs' is specified in this file, and no value is specified for 'default_change_logs',
+# then 'change_logs' MUST be specified in every entry file.
+default_change_logs: [user]
+```