Max 10k pairs per kern subtable (Fixes #1)

- Fixes script
- Adds kern diff script to compare fonts to helpers
- Moved ttfconv to helpers folder
- Updated README

helpers/kerndiff.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+
+import sys
+from fontTools.ttLib import TTFont
+
+def analyze_kern_table(font_path):
+    """
+    Loads a font and analyzes its 'kern' table, if present.
+    """
+    try:
+        font = TTFont(font_path)
+    except Exception as e:
+        print(f"Error: Could not open font file at {font_path}. Reason: {e}")
+        return
+
+    print(f"--- Analyzing 'kern' table in: {font_path} ---")
+
+    if 'kern' not in font:
+        print("No 'kern' table found.")
+        return
+
+    kern_table = font['kern']
+    print(f"  > Table version: {kern_table.version}")
+    
+    if not hasattr(kern_table, 'kernTables') or not kern_table.kernTables:
+        print("  > No subtables found.")
+        return
+
+    print(f"  > Number of subtables: {len(kern_table.kernTables)}")
+    
+    for i, subtable in enumerate(kern_table.kernTables):
+        print(f"\n  --- Subtable {i+1} ---")
+        if hasattr(subtable, 'coverage'):
+            print(f"  > Coverage flags (as integer): {subtable.coverage}")
+            # A more detailed breakdown of flags
+            coverage_int = int(subtable.coverage)
+            print(f"  > Coverage flags breakdown:")
+            print(f"    - Horizontal Kerning: {'Yes' if coverage_int & 1 else 'No'} (bit 0)")
+            print(f"    - Minimum Values: {'Yes' if coverage_int & 2 else 'No'} (bit 1)")
+            print(f"    - Cross-stream Kerning: {'Yes' if coverage_int & 4 else 'No'} (bit 2)")
+            print(f"    - Variation Kerning: {'Yes' if coverage_int & 8 else 'No'} (bit 3)")
+        
+        if hasattr(subtable, 'kernTable'):
+            print(f"  > Found {len(subtable.kernTable)} kerning pairs.")
+            # Print the first 20 kerning pairs and values for inspection
+            print("  > Sample of kerning pairs (glyph1, glyph2) -> value:")
+            for pair, value in list(subtable.kernTable.items())[:20]:
+                print(f" - ({pair[0]}, {pair[1]}) -> {value}")
+        else:
+            print("  > Subtable has no 'kernTable' attribute.")
+
+def main():
+    """
+    Main function to compare two fonts.
+    """
+    # Replace these with the actual paths to your font files
+    working_font = "./KC_Garamond-Regular.ttf"
+    broken_font = "./KF_Garamond-Regular.ttf"
+
+    analyze_kern_table(working_font)
+    print("\n" + "="*50 + "\n")
+    analyze_kern_table(broken_font)
+
+if __name__ == "__main__":
+    main()