2.0.0

Binary compatibility break

• PHP 8 support
• Symfony v6.x support
• Removed CSV support (prefer using the Symfony encoder instead).
• Deleted format ExcelEncoder::SPREADSHEET
• Added context parameter ExcelEncoder::AS_COLLECION_KEY
• Decoding without merging headers row (as no collection)
• Removed context parameter ExcelEncoder::NB_HEADER_ROWS_KEY