feat: escape all </script> that appears inside source

[icelam]

Description

Fixing issue #387 where any "</script>" string that appears inside source breaks webpage if not escaped.

How has this been tested?

1. Created a minimum webpack config and sources which contains more than 1 "</script>" string, located at __tests__/cases/escape-script-end-tag
   a. this is tested by running webpack in Jest
   b. Open the build files produced after running webpack in browser, check and make sure there is no script error

Types of changes

• New feature - feat
• Bug fix - fix
• Refactor - refactor
• Test cases - test
• Other(s):

Remarks

N/A