Add missing translations for new tram schedules table

 index.html

@@ -89,7 +89,8 @@
                    <table class="table table-condensed">
                        <thead>
                            <tr>
                                <th>Time</th> <th>Stop</th>
                                <th data-translate="header_time">Time</th>
                                <th data-translate="header_stop">Stop</th>
                            </tr>
                        </thead>
                        <tbody id="route-table">

 lang_en.js

@@ -20,6 +20,7 @@
    header_lines: 'Lines',
    header_route: 'Route',
    header_carrier: 'Carrier',
    header_stop: 'Stop',
    
    boarding_sign: '>>>',
    unknown_sign: '?',

 lang_pl.js

@@ -20,6 +20,7 @@
    header_lines: 'Linie',
    header_route: 'Trasa',
    header_carrier: 'Przewoźnik',
    header_stop: 'Przystanek',
    
    boarding_sign: '>>>',
    unknown_sign: '?',