Adding contribution file

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

Author: vincenzopalazzo

CONTRIBUTING.md

@@ -0,0 +1,49 @@
+# CONTRIBUTING
+
+Contributions are very welcome. When contributing code, please follow these
+simple guidelines.
+
+* Make happy Github actions.
+* Write properly formatted git commits (see below).
+* If you don't know where to start, look to the good first issue, or [open a discussion](https://github.com/clightning4j/JRPClightning/discussions)
+
+Git commits
+-----------
+A properly formed git commit subject line should always be able to complete the
+following sentence:
+
+     If applied, this commit will _____
+
+For example, the following message is well formed:
+
+     Add support for .gif files
+
+In addition, it should be capitalized and *must not* include a period.
+
+When it comes to formatting, here's a model git commit message[1]:
+
+     Capitalized, short (50 chars or less) summary
+
+     More detailed explanatory text, if necessary.  Wrap it to about 72
+     characters or so.  In some contexts, the first line is treated as the
+     subject of an email and the rest of the text as the body.  The blank
+     line separating the summary from the body is critical (unless you omit
+     the body entirely); tools like rebase can get confused if you run the
+     two together.
+
+     Write your commit message in the imperative: "Fix bug" and not "Fixed bug"
+     or "Fixes bug."  This convention matches up with commit messages generated
+     by commands like git merge and git revert.
+
+     Further paragraphs come after blank lines.
+
+     - Bullet points are okay, too.
+
+     - Typically a hyphen or asterisk is used for the bullet, followed by a
+       single space, with blank lines in between, but conventions vary here.
+
+     - Use a hanging indent.
+
+---
+
+[1]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html