Missing string manipulation section

[vastutsav]

refer:
https://tldp.org/LDP/abs/html/string-manipulation.html

[rawiriblundell]

A word of caution: The ABS is not highly regarded - it is outdated and promotes suboptimal practices. Its maintainer has refused to accept contributions and has refused to collaborate with others.

Reference Greg Wooledge's Wiki and the Bash Hackers Wiki instead :)

[vastutsav]

thanks