YAML linting (#3779)

.gitpod.yml

@@ -1,6 +1,8 @@
+---
 ports:
-- port: 6052
-  onOpen: open-preview
+  - port: 6052
+    onOpen: open-preview
 tasks:
-- before: pyenv local $(pyenv version | grep '^3\.' | cut -d ' ' -f 1) && script/setup
-  command: python -m esphome dashboard config
+  # yamllint disable-line rule:line-length
+  - before: pyenv local $(pyenv version | grep '^3\.' | cut -d ' ' -f 1) && script/setup
+    command: python -m esphome dashboard config