Rename, Update Docs and Prepare for Release (#9)

Co-authored-by: Guilherme Rugai Freire <41879254+GRFreire@users.noreply.github.com>
Co-authored-by: N-R-K <79544946+N-R-K@users.noreply.github.com>
Co-authored-by: NRK <nrk@disroot.org>
Co-authored-by: Arthur Williams <taaparthur@gmail.com>
Co-authored-by: eylles <ed.ylles1997@gmail.com>

CONTRIBUTING.md

@@ -0,0 +1,23 @@
+Contribution Guideline
+----------------------
+
+The scope and aim of nsxiv are:
+
+  * Bug fixes and maintenance
+  * Prioritize extensibility and simplicity
+  * Do not make the codebase more complex, keep it simple to hack on
+  * Do not add extra dependency (if we do, add compile time switch to disable it)
+  * New features may be added if it cannot be achieved (easily) via a shell script,
+    doesn't break backwards compatibility and doesn't violate any of the above rules.
+  
+When contributing, make sure:
+
+  * Your contribution falls under nsxiv's scope and aim
+  * You follow the existing code style (see [.editorconfig](.editorconfig))
+  * You open the pull request from a new branch, not from master
+
+If your contribution is not suitable for general use, it will not be included in nsxiv.
+For changes that are very much up to preference, such as changing values in config.h,
+please do not open a pull request unless you have an objective explanation.
+
+See [TODO.md](TODO.md) or the [open issues](https://github.com/nsxiv/nsxiv/issues) to find something to work on.