Added min bid increase to auction-bid-form.php

<?php
/**
 * Auction bid
 * this is modified file woocommerce-simple-auctions/templates/single-product/auction-bid-form.php
 * it should be copied to your_child_theme/woocommerce/single-product/auction-bid-form.php in order to be loaded instead of original template
 *
 */

if ( ! defined( 'ABSPATH' ) ) {
    exit; // Exit if accessed directly
}

global $product, $post;

if ( ! ( $product && $product->get_type() == 'auction' ) ) {
    return;
}
$current_user     = wp_get_current_user();
$product_id       = $product->get_id();
$user_max_bid     = $product->get_user_max_bid( $product_id, $current_user->ID );
$max_min_bid_text = $product->get_auction_type() == 'reverse' ? esc_html__( 'Your min bid is', 'wc_simple_auctions' ) : esc_html__( 'Your max bid is', 'wc_simple_auctions' );
?>

<?php if ( ( $product->is_closed() === false ) and ( $product->is_started() === true ) ) : ?>

    <?php do_action( 'woocommerce_before_bid_form' ); ?>

    <form class="auction_form cart" method="post" enctype='multipart/form-data' data-product_id="<?php echo esc_attr( $product_id ); ?>">

        <?php do_action( 'woocommerce_before_bid_button' ); ?>

        <input type="hidden" name="bid" value="<?php echo esc_attr( $product_id ); ?>" />

        <div class="quantity buttons_added">

            <input type="button" value="+" class="plus" />

            <input type="text" name="bid_value"
                data-auction-id="<?php echo esc_attr( $product_id ); ?>"
            <?php if ( $product->get_auction_sealed() != 'yes' ) { ?>
                value="<?php echo esc_attr( number_format( $product->bid_value(), wc_get_price_decimals() == 0 ? 2 : wc_get_price_decimals() , wc_get_price_decimal_separator(), wc_get_price_thousand_separator() ) ); ?>"
            <?php } ?>

            <?php
            if ($product->get_auction_sealed() != 'yes'){
                if ( $product->get_auction_type() == 'reverse' ) { ?>
                    max="<?php echo esc_attr( number_format( $product->bid_value(), wc_get_price_decimals(), wc_get_price_decimal_separator(), wc_get_price_thousand_separator() ) ); ?>"
                <?php } else { ?>
                    min="<?php echo esc_attr( number_format( $product->bid_value(), wc_get_price_decimals(), wc_get_price_decimal_separator(), wc_get_price_thousand_separator() ) ); ?>"
                <?php } ?>
            <?php } ?>
                step="<?php echo ($product->get_increase_bid_value()) ? $product->get_increase_bid_value() : '1' ?>"
                size="<?php echo strlen( $product->get_curent_bid() ) + 2; ?>"
                title="bid"
                class="input-text qty bid text left"
            />
            <input type="button" value="-" class="minus" />
        </div>

        <button type="submit" class="bid_button button alt"><?php echo apply_filters( 'bid_text', esc_html__( 'Bid', 'wc_simple_auctions' ), $product ); ?></button>

        <input type="hidden" name="place-bid" value="<?php echo esc_attr( $product_id ); ?>" />
        <input type="hidden" name="product_id" value="<?php echo esc_attr( $product_id ); ?>" />

        <?php if ( is_user_logged_in() ) { ?>
            <input type="hidden" name="user_id" value="<?php echo get_current_user_id(); ?>" />
        <?php } ?>

        <?php do_action( 'woocommerce_after_bid_button' ); ?>

    </form>

    <?php do_action( 'woocommerce_after_bid_form' ); ?>

<?php endif;