Add references to CONTRIBUTING. (#106)

Refer contributors to relevant documentation.

Author: dhebbeker

CONTRIBUTING.md

@@ -29,6 +29,10 @@ To get in touch with us you may contact a [contributor](https://github.com/Task-
 
 Before submitting to this repository, please: 
 
+* Familiarize yourself with the 
+  [software architecture documentation](<\ref software_architecture> "software architecture documentation")
+  and the
+  [design decisions](<\ref doc/decisions> "design decisions").
 * Test your contribution.
 * Make sure your code does not introduce warnings or errors.
 * Your proposition may be reviewed based on state of the art coding standards (for example [C++ Core Guidelines](https://isocpp.github.io/CppCoreGuidelines/) or [C++ Super FAQ](https://isocpp.org/faq)).

doc/decisions/README.md

@@ -1,8 +1,11 @@
 \dir .
-\brief Documentation of Decisions
+\brief \ref decision_records
+
+\page decision_records Decision Records
+\brief Documentation of decisions for the software, its architecture and design.
 
 This directory contains the documentation of design decisions made for the software.
-In particular it may contain descision records in the 
+In particular it may contain decision records in the 
 Architecture Decisions Records format described by Michael Nygard
 [here](https://cognitect.com/blog/2011/11/15/documenting-architecture-decisions).
 Those shall be kept in files named using the pattern `dr-XYZ.md`.

doc/software-architecture.md

@@ -1,4 +1,4 @@
-Software Architecture
+Software Architecture {#software_architecture}
 =====================
 
 [TOC]