feat: New page for OpenAPI security features

[SensibleWood]

This PR addresses Issue #74.

Summary of changes:

• Added Security page to specification directory.
• Provided overview of Security Scheme Object and Security Requirement Object and relationship between both.
• Provided details on each security type with examples inlne.
• Updated tictactoe OpenAPI document with examples.
• Added a note to README on running Jekyll and pointer to Contributing Guide.
• Updated link to this repository in _config.yml.
• Added diagram to represent security-related objects in digraph and SVG formats.

👍 cc @lornajane

[miqui]

@SensibleWood - have you seen this: https://swagger.io/docs/specification/authentication/

I think this is very similar to what you are proposing.

[SensibleWood]

@SensibleWood - have you seen this: https://swagger.io/docs/specification/authentication/

I think this is very similar to what you are proposing.

Yes I have read it before. I would expect there is some commonality given they are both intended to be reference materials