Add C++ Solution of "minimum-remove-to-make-valid-parentheses" & Update README.md

[yarncha]

Pull Request Template

Description

Made a stack to save left parentheses's positions.
And counted wrong parentheses with stack and made string.
Removed wrong left parentheses with elements in stack.

Put check marks:

Have you made changes in README file ?

• Added problem & solution under correct topic.
• Specified Space & Time complexity.
• Specified difficulty level, tag & Note(if any).

How Has This Been Tested?

Used this test cases to test code.

• s = "lee(t(c)o)de)"
• s = "a)b(c)d"
• s = "))(("

Make sure all below guidelines are followed else PR will get Reject:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code so that it is easy to understand
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules