fix typo and copyright (#373)

LICENSE.md

 # The MIT License
 
-Copyright © 2010–2019 Vadim Makeev, http://pepelsbey.net/
+Copyright © 2010–2021 Vadim Makeev, http://pepelsbey.net/
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 
@@ -12,7 +12,7 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 
 # Лицензия MIT
 
-Copyright © 2010–2019 Вадим Макеев, http://pepelsbey.net/
+Copyright © 2010–2021 Вадим Макеев, http://pepelsbey.net/
 
 Данная лицензия разрешает лицам, получившим копию данного программного обеспечения и сопутствующей документации (в дальнейшем именуемыми «Программное Обеспечение»), безвозмездно использовать Программное Обеспечение без ограничений, включая неограниченное право на использование, копирование, изменение, добавление, публикацию, распространение, сублицензирование и/или продажу копий Программного Обеспечения, также как и лицам, которым предоставляется данное Программное Обеспечение, при соблюдении следующих условий:
 

docs/features.md

@@ -133,7 +133,7 @@ Slide type `clear` could also hide slide number.
 
 ### Types
 
-Types are changing slide’s look. You can set type by adding class to the main `slide`. There are few built-in types available in the theme, you could also describe custom types for each presention or add it to your theme.
+Types are changing slide’s look. You can set type by adding class to the main `slide`. There are few built-in types available in the theme, you could also describe custom types for each presentation or add it to your theme.
 
 #### White
 
@@ -420,7 +420,7 @@ It can be combined with `place` class and `top` / `right` / `bottom` / `left` cl
 You can also use the `next` class for inner navigation:
 
     <section class="slide">
-        <h2>Spotlight with inner naviagation</h2>
+        <h2>Spotlight with inner navigation</h2>
         <ol>
             <li>I'll be seen right away.</li>
             <li>Just navigate to next slide and you'll see others.</li>

docs/pdf.md

 # Export to PDF
 
-Though publising your HTML slides as they are is always a better idea, you can export your presentation to PDF to upload it to a service like [SlideShare](https://www.slideshare.net/) or [Notist](https://noti.st/).
+Though publishing your HTML slides as they are is always a better idea, you can export your presentation to PDF to upload it to a service like [SlideShare](https://www.slideshare.net/) or [Notist](https://noti.st/).
 
 There are two ways of doing this: via browser print dialog or via console. Exporting via browser seems like the most convenient option, but in some cases it might take too much time or even freeze your browser if your slides are too heavy or there are too many of them.