Add necessary doc for the primer to run

Author: Pierre-Sassoulas

doc/data/messages/e/esoteric-underscore-grouping/bad.py

@@ -0,0 +1,2 @@
+having_fun = 1_23_456_7_89  # [esoteric-underscore-grouping]
+even_more_fun = 1_23_4_5_67_8e9  # [esoteric-underscore-grouping]

doc/data/messages/e/esoteric-underscore-grouping/good.py

@@ -0,0 +1,2 @@
+having_fun = 123_456_789
+even_more_fun = 1.2345678e16

doc/data/messages/u/use-standard-scientific-notation/bad.py

@@ -0,0 +1 @@
+my_number = 10e3  # [use-standard-scientific-notation]

doc/data/messages/u/use-standard-scientific-notation/good.py

@@ -0,0 +1 @@
+my_number = 1e4

doc/whatsnew/fragments/10425.feature

@@ -0,0 +1,3 @@
+Added a check for misleading scientific notations and use of underscore grouping in `float` literals.
+
+Refs #10425

tests/checkers/unittest_format.py

@@ -183,6 +183,18 @@ def test_disable_global_option_end_of_line() -> None:
         os.remove(file_.name)
 
 
+@pytest.mark.parametrize(
+    "value, expected",
+    [
+        ("0e10", "0e0"),
+        ("30e2", "3e3"),
+    ],
+)
+def test_to_standard_scientific_notation(value: str, expected: str) -> None:
+    """Test the conversion of numbers to standard underscore grouping."""
+    assert FormatChecker.to_standard_underscore_grouping(value) == expected
+
+
 @pytest.mark.parametrize(
     "value, expected",
     [