docs: add and update queries documentation (#151)

### Summary

Adds new "Queries" section inspired by https://testing-library.com/docs/dom-testing-library/api-queries

### Test plan

Reading carefully

docs/Queries.md

@@ -0,0 +1,113 @@
+---
+id: api-queries
+title: Queries
+---
+
+## Variants
+
+> `getBy` queries are shown by default in the [query documentation](#queries)
+> below.
+
+### getBy
+
+`getBy*` queries returns the first matching node for a query, and throws an
+error if no elements match.
+
+### getAllBy
+
+`getAllBy*` queries return an array of all matching nodes for a query, and
+throws an error if no elements match.
+
+### queryBy
+
+`queryBy*` queries returns the first matching node for a query, and return
+`null` if no elements match. This is useful for asserting an element is not
+present.
+
+### queryAllBy
+
+`queryAllBy*` queries return an array of all matching nodes for a query, and
+return an empty array (`[]`) if no elements match.
+
+## Queries
+
+_Note: most methods like this one return a [`ReactTestInstance`](https://reactjs.org/docs/test-renderer.html#testinstance) with following properties that you may be interested in:_
+
+```jsx
+type ReactTestInstance = {
+  type: string | Function,
+  props: { [propName: string]: any },
+  parent: null | ReactTestInstance,
+  children: Array<ReactTestInstance | string>,
+};
+```
+
+### `ByText`
+
+> getByText, getAllByText, queryByText, queryAllByText
+
+Returns a `ReactTestInstance` with matching text – may be a string or regular expression.
+
+This method will join `<Text>` siblings to find matches, similarly to [how React Native handles these components](https://facebook.github.io/react-native/docs/text#containers). This will allow for querying for strings that will be visually rendered together, but may be semantically separate React components.
+
+```jsx
+import { render } from 'react-native-testing-library';
+
+const { getByText } = render(<MyComponent />);
+const element = getByText('banana');
+```
+
+### `ByPlaceholder`
+
+> getByPlaceholder, getAllByPlaceholder, queryByPlaceholder, queryAllByPlaceholder
+
+Returns a `ReactTestInstance` for a `TextInput` with a matching placeholder – may be a string or regular expression.
+
+```jsx
+import { render } from 'react-native-testing-library';
+
+const { getByPlaceholder } = render(<MyComponent />);
+const element = getByPlaceholder('username');
+```
+
+### `ByTestId`
+
+> getByTestId, getAllByTestId, queryByTestId, queryAllByTestId
+
+Returns a `ReactTestInstance` with matching `testID` prop.
+
+```jsx
+import { render } from 'react-native-testing-library';
+
+const { getByTestId } = render(<MyComponent />);
+const element = getByTestId('unique-id');
+```
+
+## Unit testing helpers
+
+> Use sparingly and responsibly, escape hatches here
+
+`render` from `react-native-testing-library` exposes additional queries that **should not be used in component integration testing**, but some users (like component library creators) interested in unit testing some components may find helpful.
+
+<details>
+  <summary>Queries helpful in unit testing</summary>
+
+The interface is the same as for other queries, but we won't provide full names so that they're harder to find by search engines.
+
+### `ByType`
+
+> Note: added in v1.4
+
+A method returning a `ReactTestInstance` with matching a React component type. Throws when no matches.
+
+### `ByProps`
+
+A method returning a `ReactTestInstance` with matching props object
+
+### `ByName`
+
+> This method has been **deprecated** because using it results in fragile tests that may break between minor React Native versions. **DON'T USE IT**. It will be removed in next major release (v2.0). Use [`getByTestId`](#bytestid) instead. It's listed here only for back-compat purposes for early adopters of the library
+
+A method returning a `ReactTestInstance` with matching a React component type. Throws when no matches.
+
+</details>