Update a typing error (re: mixed member access) for markdown support
Summary:
Adds emphasis via markdown delimiters to a typing error message about mixed member access.
Before:
```
Typing[4064] You are trying to access the method 'bar' but this is a mixed value. Use a specific class or interface name. [1]
-> Definition is here [2]
```
After:
```
Typing[4064] You are trying to access the method 'bar' but this is a mixed value. Use a **specific** class or interface name. [1]
-> Definition is here [2]
```
This is nice simple example to show how the error formatter handles bold inside the main message (which is always bolded) by converting the desired section to bold italics.
Reviewed By: Wilfred
Differential Revision:
D23012943
fbshipit-source-id:
27ac5df23286e489f3c0283c0d38c235a4d78f1b