Add shellharden (#60)

Co-authored-by: Edwin Kofler <edwin@kofler.dev>

README.md

@@ -25,6 +25,7 @@ In addition to this list, you should read the list [awesome-shell](https://githu
 - [Defensive BASH Programming](https://web.archive.org/web/20180917174959/http://www.kfirlavi.com/blog/2012/11/14/defensive-bash-programming) - Methods to defend your programs from breaking as well as keeping the code tidy and clean.
 - [Pure Bash Bible](https://github.com/dylanaraps/pure-bash-bible) - A collection of pure bash alternatives to external processes.
 - [explainshell](https://explainshell.com) - A website that breaks down and explains shell (Bash) commands (including their flags and options).
+- [Safe ways to do things in bash](https://github.com/anordal/shellharden/blob/master/how_to_do_things_safely_in_bash.md) - How to do things safely in Bash.
 
 ## Command-Line Productivity
 
@@ -140,6 +141,7 @@ In addition to this list, you should read the list [awesome-shell](https://githu
 - [mo](https://github.com/tests-always-included/mo) - Mustache templates in pure bash.
 - [semver_bash](https://github.com/cloudflare/semver_bash) - Semantic Versioning in Bash.
 - [shellcheck](https://github.com/koalaman/shellcheck) - A static analysis tool for shell scripts.
+- [shellharden](https://github.com/anordal/shellharden) - The corrective bash syntax highlighter.
 - [shfmt](https://github.com/mvdan/sh) - Format bash programs.
 - [shunit2](https://github.com/kward/shunit2) - A unit test framework for Bash scripts with a flavour of JUnit/PyUnit.
 - [DevOps-Bash-tools](https://github.com/HariSekhon/DevOps-Bash-tools) - 750+ DevOps Shell Scripts and Advanced Bash environment.