Changed tokens and added fallback placeholders

Changed tokens and added fallback placeholders.
Previously, the tokens were %c and %(named)c, now {0} and {named}.
Added parameter placeholders for fallback insertion.
Update readme.
Update demo

Visual improvements to the project

Add readme.md
Add licence.md
Add jsdocs
Add few tests
Add demo example

The first implementation

Made the first implementation with this interface

<VueSprintf text="component say: %c">
      <ButtonUi>
        Hello!
      </ButtonUi>
</VueSprintf>