add missing context docs

Author: tsirlucas

docusaurus/docs/reactnative/contexts/theme_context.mdx

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+---
+id: theme-context
+title: ThemeContext
+---
+
+`ThemeContext` is provided by [`OverlayProvider`](../core-components/overlay_provider.mdx) and [`Chat`](../core-components/chat.mdx) components.
+Read the [theming section](../customization/theming.mdx) for more information on how to customize your theme. 
+If you are not familiar with React Context API, please read about it on [React docs](https://reactjs.org/docs/context.html).
+
+## Basic Usage
+
+`ThemeContext` can be consumed by any of the child component of `OverlayProvider` or `Chat` components.
+
+```tsx
+import { useContext } from 'react';
+import { ThemeContext } from 'stream-chat-react-native';
+
+const {
+    theme: {
+      colors: { accent_red },
+    },
+  } = useContext(OverlayContext);
+```
+
+Alternatively, you can also use `useTheme` hook provided by library to consume ThemeContext.
+
+```tsx
+import { useTheme } from 'stream-chat-react-native';
+
+const {
+    theme: {
+      colors: { accent_red },
+    },
+  } = useTheme();
+```
+
+## Value
+
+### theme
+
+The default theme object in [theme.ts](https://github.com/GetStream/stream-chat-react-native/blob/master/src/contexts/themeContext/utils/theme.ts) 
+merged with the theme you pass as `style` to [`OverlayProvider`](../core-components/overlay_provider.mdx) or [`Chat`](../core-components/chat.mdx) components. 
+
+| Type |
+| - |
+| object |

docusaurus/docs/reactnative/contexts/translation_context.mdx

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+---
+id: translation-context
+title: TranslationContext
+---
+
+`TranslationContext` is provided by [`OverlayProvider`](../core-components/overlay_provider.mdx) and [`Chat`](../core-components/chat.mdx) components. 
+Read the [translations section](../basics/translations/) for more information on how to customize your translations. 
+If you are not familiar with React Context API, please read about it on [React docs](https://reactjs.org/docs/context.html).
+
+## Basic Usage
+
+`TranslationContext` can be consumed by any of the child component of `OverlayProvider` or `Chat` components.
+
+```tsx
+import { useContext } from 'react';
+import { TranslationContext } from 'stream-chat-react-native';
+
+const { t, tDateTimeParser } = useContext(TranslationContext);
+```
+
+Alternatively, you can also use `useTranslationContext` hook provided by library to consume TranslationContext.
+
+```tsx
+import { useTheme } from 'stream-chat-react-native';
+
+const { t, tDateTimeParser } = useTranslationContext();
+```
+
+## Value
+
+### t
+
+Given a key, extracts the translated text from the Streami18n instance.
+
+| Type |
+| - |
+| function |
+
+### tDateTimeParser
+
+Used for translating dates and times into the desired local format.
+
+| Type |
+| - |
+| function |
+