Merge pull request #16 from ndaba1/lifetimes

🔃 refactor: updated the predefined theme name

📦 feat: added docs reference badge

🧹 chore: updated the changelog

📦 feat: updated the basic program bench

🔃 refactor: updated the matches struct for opts and flags

🔃 refactor: updated the options and flags references

🔃 refactor: removed lifetimes from option struct

🔃 refactor: removed the explicit lifetime in flag struct

🔃 refactor: removed tests for program settings

🔃 refactor: changed validation fn error to string

🔃 refactor: redefined the theme sruct

📦 feat: added lots of doc comments and methods

🔃 refactor: separated options and flags methods

📦 feat: added a `new_flag` function