chore: Add shebang line, -p flag to mkdir, and clean up unwanted characters in build.sh

Description:

Summary:
The build.sh script in the Rocket.Chat/apps/meteor/packages/rocketchat-livechat/plugin/ directory is missing a shebang line and fails to create directories correctly due to the absence of the -p flag with the mkdir command. Additionally, the script contains some unwanted characters that could be cleaned up.

Steps to Reproduce:

1. Navigate to Rocket.Chat/apps/meteor/packages/rocketchat-livechat/plugin/.
2. Run the build.sh script without specifying the shell explicitly.
3. Observe the errors related to directory creation and the script's execution.

Expected Behavior:

• The script should include a shebang line for proper execution.
• The mkdir command should use the -p flag to ensure parent directories are created if they do not exist.
• The script should execute without errors and create the necessary directories.

Actual Behavior:

• The script fails to run properly due to the missing shebang line.
• The mkdir command does not create directories as expected because the -p flag is missing.
• The script contains unwanted characters or formatting issues.

File Path:
Rocket.Chat/apps/meteor/packages/rocketchat-livechat/plugin/build.sh

Additional Information:

• Meteor Version: 2.16 (provided for context)

Open Rocket.Chat/apps/meteor/packages/rocketchat-livechat/plugin/build.sh and inspect the current script before running it without an explicitly specified shell. Confirm the shebang, recursive directory creation, and unwanted-character cleanup, then rerun the script and verify that it executes without errors and creates the required directories.