initial commit: The OrbTK book source tree

All files have a strong relation to the book sources of the
rust-lang project itself. This may help to lower the burden
for intrested people to get involved in OrbTK as well as
reuse workflow habits.

* LICENSE-MIT: The projekt licensing terms
* README.md: Github frontpage
* CONTIRBUTING.md: Advises on howto help improving the book
* style-guide.md: Advises on howto improve the readability of
  generated prose and code.
* tools: layout helper scripts and rust-code
* ci: continius integration helper scripts
* .gitattributes: set git default behaviours
* .gitignore: keep source tree sane
* Cargo.toml: package dependencies
* rustfmt.toml: formatting rules for rust code
* book.toml: mdBook dependencies

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>

README.md

@@ -0,0 +1,98 @@
+#  The Orbital Widget Toolkit
+
+![Build Status](https://github.com/redox-os/orbtk/book/workflows/CI/badge.svg)
+
+This repository contains the source of "The Orbital Widget Toolkit" book.
+We will further reference it as OrbTK.
+
+<!--
+	WIP: once it is ready to be shipped
+	[The book is available in dead-tree form from No Starch Press][nostarch].
+
+	[nostarch]: https://nostarch.com/
+
+	You can read the book for free online. Please see the book as shipped with
+	the latest [stable], or [develop] OrbTK releases. Be aware that issues
+	in those versions may have been fixed in this repository already, as those
+	releases are updated less frequently.
+
+	[stable]: https://doc.orbtk.org/stable/book/
+	[develop]: https://doc.orbtk.org/develop/book/
+
+	See the [releases] to download just the code of all the code listings that appear in the book.
+
+	[releases]: https://github.com/redox-os/orbtk/book/releases
+-->
+
+## Requirements
+
+Building the book requires [mdBook], ideally the same version that
+rust-lang/rust uses in [this file][rust-mdbook]. To get it:
+
+[mdBook]: https://github.com/rust-lang-nursery/mdBook
+[rust-mdbook]: https://github.com/rust-lang/rust/blob/master/src/tools/rustbook/Cargo.toml
+
+```bash
+$ cargo install mdbook --vers [version-num]
+```
+
+## Building
+
+To build the book, change into this directory and type:
+
+```bash
+$ mdbook build
+```
+
+The output will be in the `book` subdirectory. To check it out, open it in
+your web browser.
+
+_Firefox:_
+```bash
+$ firefox book/index.html                       # Linux
+$ open -a "Firefox" book/index.html             # OS X
+$ Start-Process "firefox.exe" .\book\index.html # Windows (PowerShell)
+$ start firefox.exe .\book\index.html           # Windows (Cmd)
+```
+
+_Chrome:_
+```bash
+$ google-chrome book/index.html                 # Linux
+$ open -a "Google Chrome" book/index.html       # OS X
+$ Start-Process "chrome.exe" .\book\index.html  # Windows (PowerShell)
+$ start chrome.exe .\book\index.html            # Windows (Cmd)
+```
+
+Executing `mdbook serve` will have **mdbook** act has a web service
+which can be accessed opening the following URL:  http://localhost:3000.
+
+To run the tests:
+
+```bash
+$ mdbook test
+```
+
+## Contributing
+
+We'd love your help! Please see [CONTRIBUTING.md][contrib] to learn about the
+kinds of contributions we're looking for.
+
+[contrib]: https://github.com/redox-os/orbtk/book/blob/master/CONTRIBUTING.md
+
+### Translations
+
+We'd love help translating the book! See the [Translations] label to join in
+efforts that are currently in progress. Open a new issue to start working on
+a new language! We're waiting on [mdbook support] for multiple languages
+before we merge any in, but feel free to start!
+
+[Translations]: https://github.com/redox-os/orbtk/book/issues?q=is%3Aopen+is%3Aissue+label%3ATranslations
+[mdbook support]: https://github.com/redox-os/orbtk/rust-lang-nursery/mdBook/issues/5
+
+## Spellchecking
+
+To scan source files for spelling errors, you can use the `spellcheck.sh`
+script. It needs a dictionary of valid words, which is provided in
+`dictionary.txt`. If the script produces a false positive (say, you used word
+`BTreeMap` which the script considers invalid), you need to add this word to
+`dictionary.txt` (keep the sorted order for consistency).