ENH: _font: Add method to calculate text width

This adds a method to calculate the width of a text
string. This method can later be used to wrap text
at a certain length.

Code blatantly copied from the _font.py file in the
text extractor code.

Author: PJBrs

pypdf/_font.py

@@ -35,3 +35,9 @@ def from_font_resource(cls, pdf_font_dict: DictionaryObject) -> "FontDescriptor"
         if font_name in CORE_FONT_METRICS:
             return CORE_FONT_METRICS[font_name]
         return cls(name=font_name)
+
+    def text_width(self, text: str) -> float:
+        """Sum of character widths specified in PDF font for the supplied text."""
+        return sum(
+            [self.character_widths.get(char, self.character_widths.get("default", 0)) for char in text], 0.0
+        )