Update CONTRIBUTING.md and add recommended extensions

Signed-off-by: Eddie Carswell <[email protected]>

.vscode/extensions.json

@@ -0,0 +1,3 @@
+{
+  "recommendations": ["timonwong.shellcheck", "foxundermoon.shell-format"]
+}

docs/CONTRIBUTING.md

@@ -11,13 +11,23 @@ addressed by asking instead on [Gitter].
 
 For pull requests, features and bug fixes should be submitted to the `dev`
 branch. Bug fixes will also get pushed to `master` or the relevant release
-branch when needed. Code submissions should be [lint] free, and follow best
-practices where possible.
+branch when needed. Code submissions should be lint free and follow best
+practices where possible. We use [shellcheck] and [shfmt] for this purpose. If
+you're using VSCode, it will recommend them when you open this repo.
+
+The code generally follows Google's Bash style [guide], with notable exceptions:
+
+- Indent with four spaces, no tabs. The `.editorconfig` file helps with this.
+- Pipeline and compounds (e.g. `|` or `&&`) end a line instead of beginning it.
+- Variables are brace delimited (`${var}`) only when needed, but always quoted.
+- Function namespacing is done with `.` instead of `::` (e.g. `module.func()`).
 
 By making contributions to this project you agree to follow the conditions laid
 out in the [Developer Certificate of Origin][cert].
 
 [issue]: https://github.com/AfroThundr3007730/syncrepo/issues/new
 [gitter]: https://matrix.to/#/#syncrepo:gitter.im
-[lint]: https://github.com/koalaman/shellcheck
+[shellcheck]: https://github.com/koalaman/shellcheck
+[shfmt]: https://github.com/mvdan/sh
+[guide]: https://github.com/google/styleguide/blob/gh-pages/shellguide.md
 [cert]: https://developercertificate.org/