Ignore some D rules

```
$ ruff check pygmt doc/conf.py examples --statistics
645	D200	[*] One-line docstring should fit on one line
312	D205	[ ] 1 blank line required between summary line and description
123	D400	[ ] First line should end with a period
 30	D401	[ ] First line of docstring should be in imperative mood: "A mock GMT API function that always returns a given value."
 30	D412	[*] No blank lines allowed between a section header and its content ("Examples")
 12	D202	[*] No blank lines allowed after function docstring (found 1)
```

pyproject.toml

@@ -133,6 +133,12 @@ select = [
     "YTT",  # flake8-2020
 ]
 ignore = [
+    "D200",     # One-line docstring should fit on one line
+    "D205",     # 1 blank line required between summary line and description
+    "D400",     # First line should end with a period
+    "D401",     # First line of docstring should be in imperative mood
+    "D412",     # No blank lines allowed between a section header and its content
+    "D202",     # No blank lines allowed after function docstring
     "E501",     # Avoid enforcing line-length violations
     "ISC001",   # Single-line-implicit-string-concatenation, conflict with formatter
     "PD901",    # Allow using the generic variable name `df` for DataFrames