### Describe Your Changes
- replace docs in root README with a link to official documentation
- remove old make commands for documentation
- remove redundant "VictoriaMetrics" from document titles
- merge changelog docs into a section
- rm content of Single-server-VictoriaMetrics.md as it can be included from docs/README
- add basic information to README in the root folder, so it will be useful for github users
- rm `picture` tag from docs/README as it was needed for github only, we don't display VM logo at docs.victoriametrics.com
- update `## documentation` section in docs/README to reflect the changes
- rename DD pictures, as they now belong to docs/README
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
