updated CONTRIBUTNG re naming functions

CONTRIBUTING.md

+# Welcome
+
 We welcome your [contributions](https://opensource.creativecommons.org/contributing-code/) to improving this repo.
 
 Please contribute using [branches](https://git.soton.ac.uk/SERG/workflow/-/blob/master/howTo/gitBranches.md).
@@ -5,3 +7,20 @@ Please contribute using [branches](https://git.soton.ac.uk/SERG/workflow/-/blob/
 We subscribe to the [Contributor Covenant Code of Conduct](https://www.contributor-covenant.org/version/2/0/code_of_conduct/). Please abide by it.
 
 Thank you!
+
+# Naming conventions
+
+In general we use:
+
+> [data.table](https://rdatatable.gitlab.io/data.table/)
+
+for all our data manipulation and:
+
+> <data>_<action> for our function names
+
+Thus the function to:
+
+ * load the survey file and return it as a [data.table](https://rdatatable.gitlab.io/data.table/) is `SAVEr::survey_load(f)` where f is the file path
+ * create the derived (recoded) tenure variable in the survey data is `SAVEr::survey_dv_tenure(dt)` where dt is the survey file as a [data.table](https://rdatatable.gitlab.io/data.table/)
+ 
+ 
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