fix: allow decorated properties with class fields

Allows properties decorated with lit property decorators to have class
fields alongside.

This loosens the strictness of the rule under the assumption you have
set `useDefineForClassFields: false` in typescript.

If you use `declare` or `accessor`, those fields will already be ignored
by this rule.

Examples:

```ts
// Error
class X extends LitElement {
  fieldA;
  static properties = {fieldA: {type: String}};
}

// Works now, errored before
class X extends LitElement {
  @Property()
  fieldA;
}

// Worked before, works now
class X extends LitElement {
  @Property()
  declare fieldA;
}

// Worked before, works now
class X extends LitElement {
  declare fieldA;
  static properties = {fieldA: {type: String}};
}

// Worked before, works now
class X extends LitElement {
  @Property()
  accessor fieldA;
}
```

Fixes #193.

docs/rules/no-classfield-shadowing.md

@@ -1,11 +1,11 @@
-# Disallows class fields with same name as static properties
+# Disallows class fields with same name as reactive properties
 
-Class fields set with same names as static properties will not trigger updates as expected. They will overwrite
+Class fields set with same names as reactive properties will not trigger updates as expected. They will overwrite
 accessors used for detecting changes. See https://lit.dev/msg/class-field-shadowing for more information.
 
 ## Rule Details
 
-This rule disallows class fields with same name as static properties.
+This rule disallows class fields with same name as reactive properties.
 
 The following patterns are considered warnings: