This pull request introduces a new input processing mode to the purl tool, allowing it to handle data on a line-by-line basis. The changes include updates to the documentation, the command-line interface, and the test cases to support this new mode.

Documentation Updates:

• Added a new section "Input Processing Modes" to the README.md file, explaining the two ways purl can read input: Multi-Line Mode for files and Line Mode for standard input.

Command-Line Interface Updates:

• Introduced a new lineMode flag to the CLI struct in internal/cli/cli.go.
• Updated the parseFlags method to handle the new -line option and automatically enable line mode when reading from standard input. [1] [2]
• Modified the replaceProcess and extractProcess methods to support line-by-line processing when lineMode is enabled. [1] [2] [3]

Test Case Updates:

• Added new test cases in internal/cli/cli_test.go to verify the functionality of the line mode, including tests for line-by-line replacement and extraction. [1] [2] [3] [4]