Update .readthedocs.yaml

./.readthedocs.yaml
  Warning: 5:1 [document-start] missing document start "---"
  Error: 16:81 [line-length] line too long (110 > 80 characters)
  Error: 30:4 [indentation] wrong indentation: expected 2 but found 3
  Error: 32:50 [new-line-at-end-of-file] no new line character at the end of file

.readthedocs.yaml

@@ -1,3 +1,4 @@
+---
 # Read the Docs configuration file for Sphinx projects
 # See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
 
@@ -13,7 +14,8 @@ build:
 # Build documentation in the "docs/" directory with Sphinx
 sphinx:
   configuration: docs/conf.py
-  # You can configure Sphinx to use a different builder, for instance use the dirhtml builder for simpler URLs
+  # You can configure Sphinx to use a different builder,
+  # for instance use the dirhtml builder for simpler URLs
   # builder: "dirhtml"
   # Fail on all warnings to avoid broken references
   fail_on_warning: true
@@ -27,6 +29,6 @@ sphinx:
 # to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
 python:
-   install:
-     - requirements: requirements.txt
-     - requirements: docs/sphinx_requirements.txt
+  install:
+    - requirements: requirements.txt
+    - requirements: docs/sphinx_requirements.txt