doc: add Russian tutorial (#283)

Author: AABur

CHANGELOG.md

@@ -19,7 +19,7 @@ and [PEP 440](https://www.python.org/dev/peps/pep-0440/).
 
     5. [Creating Tables](https://pyfpdf.github.io/fpdf2/Tutorial.html#tuto-5-creating-tables)
     6. [Creating links and mixing text styles](https://pyfpdf.github.io/fpdf2/Tutorial.html#tuto-6-creating-links-and-mixing-text-styles)
-- New translation of the tutorial in Hindi, thanks to @Mridulbirla13: [हिंदी संस्करण](https://pyfpdf.github.io/fpdf2/Tutorial-हिंदी.html); [Deutsche](https://pyfpdf.github.io/fpdf2/Tutorial-de.html), thanks to @digidigital; and [Italian](https://pyfpdf.github.io/fpdf2/Tutorial-it.html) thanks to @xit4
+- New translation of the tutorial in Hindi, thanks to @Mridulbirla13: [हिंदी संस्करण](https://pyfpdf.github.io/fpdf2/Tutorial-हिंदी.html); [Deutsche](https://pyfpdf.github.io/fpdf2/Tutorial-de.html), thanks to @digidigital; and [Italian](https://pyfpdf.github.io/fpdf2/Tutorial-it.html) thanks to @xit4; and [Русский](https://pyfpdf.github.io/fpdf2/Tutorial-ru.html) thanks to @AABur
 - While images transparency is still handled by default through the use of `SMask`,
   this can be disabled by setting `pdf.allow_images_transparency = False`
   in order to allow compliance with [PDF/A-1](https://en.wikipedia.org/wiki/PDF/A#Description)

README.md

@@ -81,7 +81,7 @@ Documentation:
 --------------
 
 - [Documentation Home](https://pyfpdf.github.io/fpdf2/)
-- Tutorial in several languages: [English](https://pyfpdf.github.io/fpdf2/Tutorial.html) - [Deutsche](https://pyfpdf.github.io/fpdf2/Tutorial-de.html) - [Spanish](https://pyfpdf.github.io/fpdf2/Tutorial-es.html) - [हिंदी](https://pyfpdf.github.io/fpdf2/Tutorial-हिंदी.html) - [Italian](https://pyfpdf.github.io/fpdf2/Tutorial-it.html)
+- Tutorial in several languages: [English](https://pyfpdf.github.io/fpdf2/Tutorial.html) - [Deutsche](https://pyfpdf.github.io/fpdf2/Tutorial-de.html) - [Spanish](https://pyfpdf.github.io/fpdf2/Tutorial-es.html) - [हिंदी](https://pyfpdf.github.io/fpdf2/Tutorial-हिंदी.html) - [Italian](https://pyfpdf.github.io/fpdf2/Tutorial-it.html) - [Русский](https://pyfpdf.github.io/fpdf2/Tutorial-ru.html)
 - Release notes: [CHANGELOG.md](https://github.com/PyFPDF/fpdf2/blob/master/CHANGELOG.md)
 
 You can also have a look at the `tests/`, they're great usage examples!