Woocommerce Payment Gateway Based Fees 5.1.4

* fixed: "Trying to access array offset on value of type null for $fee->gateway_option[WC_Add_Fees::OPT_KEY_OUTPUT]" on checkout page for very small values when fee amount = 0
* checked compatibility for WP 6.6 and WooCommerce 9.2.3
* correction below filter "wc_add_fees_wc_fees_calculated_done_check" was "wc_add_fees_wc_calculated_totals_done_check"
Open-Library/Payment Gateway Based Fees/Fee Calculation/wc_add_fees_wc_calculated_totals_done_check.php at main · InoplugsOrganization/Open-Library

* feature: option "Maximum fee": limit fee to a maximum value
* feature: option "Exclude Fees For E-Mails": skip total cart fees for a gateway for given E-Mails
* added: filter "wc_add_fees_gateway_fee_maximum": change maximum fee value during calculation
* added: filter "wc_add_fees_hide_product_panel_options": remove our tab from product metabox settings
Open-Library/Payment Gateway Based Fees/Metabox Product/wc_add_fees_hide_product_panel_options.php at main · InoplugsOrganization/Open-Library
* added: filter "wc_add_fees_wc_fees_calculated_done_check": skip a second fee calculation (e.g. by WC automatic tax calculation)
Open-Library/Payment Gateway Based Fees/Fee Calculation/wc_add_fees_wc_fees_calculated_done_check.php at main · InoplugsOrganization/Open-Library

* fixed: small typo error
* fixed: minor styling error in backend product tab fees settings
* fixed: Warning: Undefined variable $index in ../classes/class-wc-add-fees.php on line 920