Show the code surrounding the position of a parse error

[yannham]

Is your feature request related to a problem? Please describe.
Parse errors could be more user-friendly. They currently include the location of the problem, but do not take advantage of the error reporting infrastructure which is capable of showing the incriminated snippet. Compare this:

$nickel <<< '%a" '
error: While parsing: Invalid token at 870

to a type error:

error: Type error
  ┌─ <stdin>:1:5
  │
1 │ 1 + "a"
  │     ^^^ This expression has type Str, but Num was expected
  │
  = +, 2nd argument

Describe the solution you'd like
Parse errors show the incriminated snippets, as do evaluation errors:

$nickel <<< '%a" '
error: Parse error
  ┌─ <stdin>:1:5
  │
1 │ %a"
  │ ^ Invalid token