add prettier as non-code auto formatter

.pre-commit-config.yaml

@@ -3,19 +3,23 @@ repos:
     rev: v4.0.1
     hooks:
       - id: check-docstring-first
-      - id: check-toml
-      - id: check-yaml
-        exclude: packaging/.*
       - id: mixed-line-ending
         args: [--fix=lf]
       - id: end-of-file-fixer
 
-  # - repo: https://github.com/asottile/pyupgrade
-  #   rev: v2.29.0
-  #   hooks:
-  #     - id: pyupgrade
-  #       args: [--py36-plus]
-  #       name: Upgrade code
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v2.5.1
+    hooks:
+      - id: prettier
+        types_or:
+          - markdown
+          - toml
+          - yaml
+        exclude: |
+          (?x)^(
+              .circleci/config.yml|
+              packaging/.*
+          )$
 
   - repo: https://github.com/omnilib/ufmt
     rev: v1.3.0

.prettierrc.yaml

@@ -0,0 +1,2 @@
+proseWrap: always
+printWidth: 120