Accept .codecov.yml as an alternative to codecov.yml #2996

spec/files.json requires codecov.yml at the repository root. Please also accept .codecov.yml, which Codecov reads from the same place (Codecov docs).

Why: ptr727/ESPHome-Config is the live /config directory of an ESPHome instance. The ESPHome device builder treats every root *.yml/*.yaml file as a device config, so codecov.yml shows up as a device in the dashboard.

• The scan is ESPHome core's filter_yaml_files in esphome/util.py. It skips only secrets.yaml/secrets.yml and dotfiles, and it has no ignore mechanism.
• Upstream treats this as intended ([Bug] Partial YAML files in the root directory are treated as devices esphome/device-builder#1259, closed not planned), and The way to ignore yaml file in configuration directory esphome/feature-requests#2528 asks for an ignore option, so an upstream fix is not expected.
• A dotfile name is the only way to hide the file while keeping it in the root.

Ask: accept .codecov.yml as an alternative path for the codecov.yml entry, in the spec, the audit, and the WORKFLOW.md D1.6 wording.

Follow-up: once the hub supports it, rename codecov.yml to .codecov.yml in ptr727/ESPHome-Config.