README update, add CONTRIBUTING

Remove upcoming changes since nothing backward-incompatible is
upcoming, and OS and Linux distro support is already specified in
pinned issue.

CONTRIBUTING.org

@@ -0,0 +1,87 @@
+#+title: Contributing
+#+author: Lucien Cartier-Tilet
+#+email: lucien@phundrak.com
+First of all, thank you for being interested in contributing! You rock!
+
+In this document, you will find some guidelines for contributing to
+~eshell-info-banner.el~. These are more guidelines than rules, so don’t
+try too hard to follow them.
+
+* Table of Contents                                                :TOC_5_gh:
+- [[#how-can-i-contribute][How Can I Contribute?]]
+  - [[#submitting-bugs-and-errors][Submitting Bugs and Errors]]
+  - [[#submitting-new-code][Submitting New Code]]
+    - [[#git-commit-messages][Git Commit Messages]]
+    - [[#describing-the-pull-request][Describing the Pull Request]]
+  - [[#finding-something-to-do][Finding Something To Do]]
+- [[#issue-labels][Issue Labels]]
+
+* How Can I Contribute?
+** Submitting Bugs and Errors
+The easiest way to contribute is to the project is if you encounter a
+bug or an error. If you encounter one, check whether there is an issue
+already opened. If not, you can open one! Try to provide as much
+information as possible:
+- Are you running the latest version of the package?
+- Which version of Emacs are you running? On what system?
+- What is your configuration for this package?
+- What is the error message? Do you have a debug trace for the error?
+- Can you reproduce it consistently? If so, how?
+- What would the expected behavior be?
+As you are collecting these pieces of information, try to come up with
+a short and clear issue title –it should describe quickly your issue
+without being too vague (e.g. avoid stuff like “error when opening
+Eshell” or “doesn’t work”).
+
+** Submitting New Code
+If you are submitting new code through a pull request, make sure of
+the following:
+- Your code doesn’t do something already implemented in the package
+- Your code follows the Emacs Lisp style guide presented [[https://github.com/bbatsov/emacs-lisp-style-guide][here]] as best
+  as you can
+- All new functions and variables declared through ~defvar~, ~defcustom~,
+  and ~defconst~ have docstrings
+- If you introduced new dependencies in your code, you also added them
+  to the list of dependencies in the file’s headers
+- And obviously, your code works (I include that because I myself
+  sometimes push commits that don’t work)
+
+*** Git Commit Messages
+Your commits should also follow [[https://github.com/syl20bnr/spacemacs/blob/develop/CONTRIBUTING.org#commit-messages][Spacemacs’ guidelines]] on this matter,
+especially:
+- Lines no longer than 72 characters
+- Explain what you did
+- Use the imperative in your summary
+- Use present tense and imperative for what your commit changes
+
+*** Describing the Pull Request
+When opening a new pull request, check that its title is short and
+clear as to what it is meant to do. Its description should:
+- Provide the current behavior of the package, and how it will modify it
+- If it is linked to an open issue, mention it
+- If you are submitting an enhancement pull request, describe why this
+  code suggestion would be useful
+
+** Finding Something To Do
+Not sure where to begin? Take a look at the list of open issues,
+especially the ones with one of the following labels:
+- [[https://github.com/Phundrak/eshell-info-banner.el/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc+label%3A%22good+first+issue%22][/good first issue/]] :: These issues indicate easy to fix issues and
+  easy to implement enhancements. If you are a beginner or if you want
+  to familiarize yourself with the package, look for these issues.
+- [[https://github.com/Phundrak/eshell-info-banner.el/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22+sort%3Aupdated-desc][/help wanted/]] :: These issues might require some more work than /good
+  first issue/ issues and might be a bit more interesting.
+If you want to work on an open issue, leave a comment saying
+so. However, you can directly submit a pull request if you are simply
+adding support for a non-standard Linux distribution.
+
+* Issue Labels
+| Label            | Description                                                         |
+|------------------+---------------------------------------------------------------------|
+| enhancement      | Feature request                                                     |
+| good first issue | easy to fix issue                                                   |
+| bug              | Confirmed bug or something very likely to be a bug                  |
+| help wanted      | This bug might not be my priority, so feel to give it a try!        |
+| documentation    | There is something wrong with the documentation                     |
+| duplicate        | The issue has already been reported                                 |
+| invalid          | Issue isn’t valid (not the package’s fault)                         |
+| wontfix          | It’s either working as intended, or I decided not to fix it for now |