docs: add removal of theme default prop ADR

docs/adrs/002-theme-default-prop-removal.md

@@ -0,0 +1,34 @@
+# ADR-002: Removal of Default Theme Property in Components
+
+2024-09-06
+
+## Context
+
+Garden is a suite of React components distributed across various NPM packages, all crafted using TypeScript, React, and styled-components for CSS. Each component in Garden relies on a `theme` object for styling, which was previously provided through two methods:
+
+- **defaultProps:** Components used a static `DEFAULT_THEME` object as a default property, allowing them to render with predefined styles without explicit theme provision.
+- **React Context API:** Components could also receive the `theme` dynamically via a `ThemeProvider`, which encapsulates components and passes the `theme` object through context, allowing real-time theme updates.
+
+With the introduction of a light/dark mode feature in version 9, dynamic theming has become essential. This shift necessitates that all components must now dynamically receive the theme, making the static `defaultProps` approach obsolete.
+
+## Decision
+
+From version 9 onwards, Garden components will no longer accept the theme object via `defaultProps`. Instead, all components must be nested within a `ThemeProvider` to receive the theme through React's context API. This change ensures:
+
+- A unified source for theming, preventing discrepancies and maintenance issues.
+- Enhanced support for dynamic theme changes, crucial for features like light/dark modes.
+
+## Consequences
+
+### Positive
+- **Consistency and Single Source of Truth:** By mandating the `ThemeProvider`, we establish a single, consistent method for theme distribution, avoiding confusion and potential conflicts from dual theme sources.
+- **Dynamic Theming Support:** This alteration is vital for dynamic theming scenarios where themes can change in real-time, ensuring all components update uniformly.
+- **Alignment with Industry Standards:** Garden now aligns with the practices of other leading React libraries, reducing the learning curve for developers familiar with similar ecosystems.
+
+### Negative
+- **Migration Effort:** Users upgrading from v8 to v9 will need to wrap their Garden components with `ThemeProvider`.  This adjustment may require some effort, but it simplifies long-term maintenance and enhances flexibility in theming.
+
+By enforcing the use of `ThemeProvider`, Garden not only adopts a robust and scalable approach to theming but also adheres to contemporary React development best practices, enhancing both user experience and developer productivity.
+
+### Links
+**Reference PR:** https://github.com/zendeskgarden/react-components/pull/1905 

docs/adrs/README.md

@@ -4,3 +4,4 @@ Garden architectural decison records (ADRs) capture important decisions made,
 along with context and consequences.
 
 - [ADR-001](./001-theming-peer-dependency.md): Theming peer dependency
+- [ADR-002](./002-theme-default-prop-removal.md): Removal of `theme` default prop