Fix Russian README

In Russian README, "Вложенные шаблоны" -> "Включённые шаблоны"
Move "Embedded Templates" subsection in README

Move "Embedded Templates" subsection in English and Russian README to a more appropriate place.
"Embedded Templates" -> "Literal Templates"

In English and Russian README, rename "Embedded Templates" to "Literal Templates".
Tests: 5 template helpers can nest layouts
Allow 5 template helpers to take a block
Add README section on new way of nesting layouts

Add README section "Templates with `yield` and nested layouts" in English and Russian.