docs: documentation and naming consistency fixes

[kamajus3]

Problems

1. Naming Consistency: The primary class of the library, originally named "OtpInput," was inconsistently referred to as "OTPInput" in the documentation. This pull request standardizes the naming to "OtpInput" throughout the documentation for clarity and consistency.

2. Documentation Structure Improvement: The documentation contained an error in the structure for configuring the component. Certain properties needed to be nested within the "theme" property to enhance organization and clarity. This pull request corrects the documentation structure, improving its readability and ease of use.

Proposed Changes:

• Update references from "OTPInput" to "OtpInput" in the documentation.
• Restructure the documentation example code to correctly group related properties within the "theme" object.

#11

[techieoriname]

Thank you @carl0smat3us.
Really nice, it's great effort put in so far.
There's actually more to just the documentation

[anday013]

@carl0smat3us nice catches! Thank you for your contribution!