docs: update PDF set

See merge request picodata/picodata/docs!45

docs: update site and product description

See merge request picodata/picodata/docs!44

docs: added user manual PDF

See merge request picodata/picodata/docs!43

docs: added install guide in PDF

See merge request picodata/picodata/docs!42

docs: fix discovered typos

See merge request picodata/picodata/docs!41

feat: expel node

See merge request picodata/picodata/docs!40

docs: fix typos and minor flaws

See merge request picodata/picodata/docs!39

docs: update structure, add compilation steps

See merge request picodata/picodata/docs!38

docs: complement instance-id description

See merge request picodata/picodata/docs!37

docs: mention CentOS 8 support

See merge request picodata/picodata/docs!36

docs: update download info in install.md

See merge request picodata/picodata/docs!35

Fix

See merge request picodata/picodata/docs!34

docs: revise install.md

See merge request picodata/picodata/docs!33

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