Repository: sqlfluff/sqlfluff

Issue:
Whitespace token is_whitespace is False
I expect segment.is_whitespace of a Whitespace token is True, however, it is set to False.

## Expected Behaviour
segment.is_whitespace return True

## Observed Behaviour
segment.is_whitespace return False
## Steps to Reproduce

## Version
Include the output of `sqlfluff --version` along with your Python version

## Configuration
```
Include your SQLFluff configuration here
```


Discussion:

Patch:
diff --git a/src/sqlfluff/core/rules/base.py b/src/sqlfluff/core/rules/base.py
index 197686231..457aaff3e 100644
--- a/src/sqlfluff/core/rules/base.py
+++ b/src/sqlfluff/core/rules/base.py
@@ -404,7 +404,9 @@ class BaseRule:
     @classmethod
     def make_whitespace(cls, raw, pos_marker):
         """Make a whitespace segment."""
-        WhitespaceSegment = RawSegment.make(" ", name="whitespace", type="whitespace")
+        WhitespaceSegment = RawSegment.make(
+            " ", name="whitespace", type="whitespace", is_whitespace=True
+        )
         return WhitespaceSegment(raw=raw, pos_marker=pos_marker)
 
     @classmethod


Test patch:
diff --git a/test/core/rules/base_test.py b/test/core/rules/base_test.py
new file mode 100644
index 000000000..831460410
--- /dev/null
+++ b/test/core/rules/base_test.py
@@ -0,0 +1,7 @@
+"""Test sqlfluff.core.rules.base module."""
+import sqlfluff.core.rules.base as rules_base
+
+
+def test_whitespace_segment_is_whitespace():
+    """Tests that WhitespaceSegment.is_whitespace is True."""
+    assert rules_base.BaseRule.make_whitespace("", "").is_whitespace