[devhelp] docs: add similar-apps page

[Sébastien Wilmet <swilmet src gnome org>]

commit 2c740cb014d3f5f4e604cdeb4aaea170fa0e8dc9
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Apr 26 21:08:40 2020 +0200

    docs: add similar-apps page
    
    It was initially on the Devhelp wiki.

 docs/similar-apps.md | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/docs/similar-apps.md b/docs/similar-apps.md
new file mode 100644
index 00000000..b8f4427c
--- /dev/null
+++ b/docs/similar-apps.md
@@ -0,0 +1,8 @@
+Similar apps to Devhelp
+=======================
+
+Can serve as inspiration to develop Devhelp.
+
+- [Dash](https://kapeli.com/dash) (macOS)
+- [Zeal](https://zealdocs.org/)
+- [ZevDocs](https://github.com/jkozera/zevdocs) - a fork of Devhelp with support for zealcore