[feature request] Allow inputs to span multiple lines

[gtg922r]

Considering allowing inputs to span across multiple lines, potentially by including a \ at the end of a line.

For example

 _```math
a_nice_long_variable = another_variable + \
$100,000 + $1,000
_```

should evaluate without an error, and set a_nice_long_variable equal to another_variable + $100,000 + $1,000

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