docs: refactor button and modal builder examples

[DCodeProg]

This pull request updates the documentation for Discord component APIs to reflect new naming conventions and usage patterns, especially around modals and message building. The changes improve clarity and consistency in the code examples and terminology, making it easier for developers to use the library correctly.

Component API updates:

• Replaced all instances of MessageComponentBuilder with MessageBuilder in examples, reflecting the updated API for constructing messages with components. [1] [2] [3] [4] [5] [6] [7]
• Changed usages of MessageMenu to SelectMenu for building select menu components, aligning with new naming conventions. [1] [2]

Modal/dialog terminology and usage:

• Replaced all references to "dialog" with "modal" throughout the documentation, including class names, event names, and example code, to match Discord's terminology and the updated API. [1] [2]
• Updated modal builder examples to use ModalBuilder and demonstrate new modal features, such as markdown text, labels, descriptions, and component configuration.
• Updated event handling examples to use ServerModalSubmitEvent and related modal event handlers instead of dialog events. [1] [2]

Code formatting improvements:

• Improved readability of button builder examples by formatting constructor arguments and using consistent code style.