Add debug documentation

[pyrmont]

@miparnisari wrote in a comment in #1111:

Can we add information on how to debug while developing? What I do is run rackup >> debug.txt and then load localhost:9292/json?debug which prints something like

lexer: json
stack: [:root]
stream: "\"firstName\": \"John\","
  trying #<Rule /\s+/m>
  trying #<Rule /"/>
    got "\""
    yielding Literal.String.Double, "\""
    pushing :string
lexer: json
stack: [:root, :string]
stream: "firstName\": \"John\",\n"
  trying #<Rule /[^\\"]+/>
    got "firstName"
    yielding Literal.String.Double, "firstName"

[stale]

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[pyrmont]

This is still outstanding.

[ComFreek]

I just found this issue and found it helpful for debugging. It's not stale!

Any tips on how to best human-parse the output on CLI? The first time I go to localhost:9292/json?debug, it's all just fine parsable, but then I usually go on to fix something in the lexer and refresh the page. Then the CLI is spammed with another round of debug info and I cannot determine what's old and what's new debug info anymore.
Does anyone got some shell tricks (e.g. with less)?

[stale]

This issue has been automatically marked as stale because it has not had any activity for more than a year. It will be closed if no additional activity occurs within the next 14 days.
If you would like this issue to remain open, please reply and let us know if the issue is still reproducible.