Cannot style <Text> within <Text>
_I am..._

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| Reporting a bug or issue
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**Expected behavior:**

A multiline block of text should be able to have an arbitrary word (or words) within it styled separately. i.e.

The quick brown fox\n
jumped over **the**\n
lazy dog

Here the newlines are added for clarity to show where the text might be forced to wrap.

**Observed behavior:**

This just isn't possible. Attempting to nest `<Text>` within `<Text>` results in the following error:

`Error: "sketch_text" is not a valid child for Text components`

**How to reproduce:**

Try to render this code:

`<Text style={{...}}>Text styled one way,<Text style={{...}}>text styled another way.</Text></Text>`

**Sketch version:**

61.2

I feel like this is a reasonable thing to request, because not being able to do so significantly hampers the ability to design things like the following:

<img width="273" alt="Screen Shot 2020-01-20 at 5 13 26 PM" src="https://user-images.githubusercontent.com/113397/72767223-39e3db00-3ba8-11ea-830d-734d6e87eb76.png">

