Add Developer guide to documentation

Change-Id: I960370076653737b9d2892ce657015cd5f8025ea
Issue-ID: CCSDK-2833
Signed-off-by: elinuxhenrik <henrik.b.andersson@est.tech>
diff --git a/.gitignore b/.gitignore
index e4d2870..fe1a055 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,6 +21,8 @@
 **/yang-gen-sal
 *.interp
 sli/model/src/main/java
+node_modules
+package-lock.json
 
 ## Misc Ignores (OS specific etc) ##
 bin/