[evince] Updated Contribution Guidelines

[Germán Poo-Caamaño <gpoo src gnome org>]

commit e13339c8ee1dc0bf876d2af466f287215a2370a9
Author: Pranali Deshmukh <pranali21293 gmail com>
Date:   Thu Jul 2 04:16:31 2020 +0530

    Updated Contribution Guidelines
    
    Added line width recommendation for commit descriptions to the contribution
    guidelines.

 CONTRIBUTING.md | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 2c8b8fb5..25744bd7 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -167,6 +167,11 @@ Closes #1234
  down the line) detailing **why** you changed something. There's no need
  to specify the **how**: the changes can be inlined.
 
+ - While adding the main description please make sure that individual lines 
+within the body are no longer than 80 columns, ideally a bit less. This makes
+it easier to read without scrolling (both in GitLab as well as a terminal with 
+the default terminal size).
+
  - When committing code on behalf of others use the `--author` option, e.g.
  `git commit -a --author "Joe Coder <joe coder org>"` and `--signoff`.