Add[#124]: local-exec multi command example

[vivekvr1]

Closes: #124

Be noted that 124 is the issue ID

What is the purpose of the change

Changes:

• Added a new folder called multi-command under getting-started/local-exec.
• Copied the main.tf file from the single-command example to the new multi-command folder.
• Replaced the command section of the local-exec provisioner in the main.tf file with a multi-line command.

Add a description of the overall background and high level changes that this PR introduces

• This pull request adds a new example to the tungbq/aws-lab-with-terraform repository to execute multi-line commands using the local-exec provisioner. This example will be helpful for users who need to run more complex commands on their local systems.

(E.g.: This pull request improves documentation of area A by adding ....)

[tungbq]

Thanks @vivekvr1, it looks good.
Did you run test for this change?