docs: update materials for the new release

See merge request picodata/picodata/docs!32

docs: revise top-level structure

See merge request picodata/picodata/docs!31

* delete arch.md
* delete startup.md (unused)
* rename deploy.md caption

docs: follow-up fixes

See merge request picodata/picodata/docs!30

docs: improve newly added materials

See merge request picodata/picodata/docs!29

docs: fix URL in headerbar logo

See merge request picodata/picodata/docs!28

docs: preparing for release

See merge request picodata/picodata/docs!27

docs: set GA tag within the Material theme

See merge request picodata/picodata/docs!26

docs: make URLs open in new tabs, fix invalid URLs

See merge request picodata/picodata/docs!25

reworded app and schema dependency description

See merge request picodata/picodata/docs!24

Hits badge is now invisible

See merge request picodata/picodata/docs!23

A slew of fixes

See merge request picodata/picodata/docs!22

Restored Google global site tag

See merge request picodata/picodata/docs!21

Added simple hits counter to the main docs page

See merge request picodata/picodata/docs!20

Fixes in arch.md

See merge request picodata/picodata/docs!19

Fixed miserable typo

See merge request picodata/picodata/docs!18

Added Yandex Metrika script

See merge request picodata/picodata/docs!17

Added experimental adblock detector script

See merge request picodata/picodata/docs!16

Fixed mkdocs.yml

See merge request picodata/picodata/docs!15

New subsestion for Picodata architecture description

See merge request picodata/picodata/docs!14

# Conflicts:
#   mkdocs.yml