Update Roadmap.md (#958)

* Update Roadmap.md

Roadmap updated in accordance with the internal document

* Fix markdown issues in Roadmap

Add Roadmap.md to markdownlint check in CI

* Change name of Roadmap file to capital letters

It's more tradiotonal to name info files in uppercase
See:
https://softwareengineering.stackexchange.com/a/301708/359643

Co-authored-by: Pavel Lobashov <shockwavenn@gmail.com>

ROADMAP.md

@@ -0,0 +1,90 @@
+# ONLYOFFICE Document Server roadmap
+
+This document provides the roadmap of the planned ONLYOFFICE Document Server changes.
+
+This is an updated and corrected version of the roadmap.
+We also reserve the right to change it when necessary.
+
+## Version 6.0
+
+### All editors
+
+* 3D in autoshapes and pictures
+* Mobile versions improvements
+* Equation editor autocorrect
+* Border styles (double)
+* Paste Options (Keep Source Formatting, Merge Formatting, Keep Text Only etc.)
+* Document templates
+* Undo/redo for fast collaborative editing
+* Protecting parts of documents from being edited/copied
+* Multiple clipboard
+* Plugins development
+
+### Document editor
+
+* New content controls for filling forms
+* Table of contents for tables and images
+* Endnotes
+* The exact height of the rows in the table
+* Support of % in brush
+* Backgrounds
+* Different underlining (double line, wavy line, etc)
+* Frames for pictures and templates
+* Shadow for pictures
+* Inextricable paragraph (wrap)
+* Drawing Canvas support
+
+### Spreadsheet editor
+
+* Speedup
+* Effects
+* Backgrounds
+* Adjustable cell format (numerical, monetary, etc)
+* Improvement of auto-filters (there are no settings of
+  style parameters for spreadsheets, spreadsheet resize using mouse,
+  the auto-adding of lines within the formatted spreadsheets)
+* Version History
+* Review
+* Formulas improvements (new formulas  + speedup + wizard)
+* Pivot tables
+* Pivot charts
+* Data (Drop-down lists)
+* Sheet and data protection
+* Conditional formatting (correct display for
+  data bars formatting, support for gradient for data bars)
+* Slicers (without pivot support)
+* Autofilling algorithm  modification (adding various options,
+  for example, copy formatting only)
+* Forms
+
+### Presentation editor
+
+* Auto-fit text size in AutoShape
+* Themes and theme editor
+* Vertical text
+* Animations
+* SmartArt support
+
+### Interface
+
+* Adding the information about updates in a new version
+* Toolbar adaptation for various screen resolutions
+* Customization
+
+### Desktop and mobile editors
+
+* Development of interface for document editor for Windows, Mac, Ubuntu
+* Development of SDK presentation editor for Windows, Mac OS, iOS platforms
+* Development of SDK spreadsheet editor for Windows, Mac OS, iOS platforms
+* Development of interface for presentation editor for iPad
+* Development of SDK document and spreadsheet editors for Android
+* Development of interface for document editor for Android
+* Development of SDK presentation editor for Android
+* Development of interface for presentation editors for Android
+* Development of co-editing for document editor for iPad
+* Development of co-editing for spreadsheet editor for iPad
+* Print preview in the desktop editors
+
+### Backend
+
+* Scalability and clustering for commercial builds