Printer prepending instead of appending (#145)

* Pointing `swift-custom-dump` to the "main" branch, since `0.4.0` hasn't been released publicly yet.

* Switched printing to `prepend` rather than `append`

Consequentially, all parsers that compose multiple parsers work backwards through provided parsers, and the `input` is built up from the back to the front.

This allows print to check that the output is correct for cases like `Rest`, `Prefix`, `Not`, and `Peek`.

* Added `Many` tests, fixed terminator bug

* Whitespace cleanup

* Fixed typo in test name.

* Updated `End` to check input when printing.

Added related tests.

* Switched `Literal` printing to append rather than insert

They now append into a copy of themselves, then append the `input`.

* Updated `PrependableCollection` to use `append` internally

* Improved error output for OneOfMany

* Adds backtracking to `Optionally`

* Added unit test to check backtracking

* Updated the `testBacktracking` case

Makes it clearer under what circumstances it will fail without backtracking.

* Added backtracking to Optionally

Also updated documentation about backtracking in general.

* Removed incorrectly merged test case.

* Added `Expect`

Which can be both parsed and printed.

* Made the unexpected `Peek` success a passing test

Added notes about why it doesn't throw an error.

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* Update README.md

Co-authored-by: Brandon Williams <[email protected]>

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Co-authored-by: Stephen Celis <[email protected]>
Co-authored-by: Stephen Celis <[email protected]>
Co-authored-by: Brandon Williams <[email protected]>

Author: 3 people

Package.swift

@@ -12,7 +12,7 @@ let package = Package(
     .library(
       name: "_URLRouting",
       targets: ["_URLRouting"]
-    )
+    ),
   ],
   dependencies: [
     .package(url: "https://github.com/apple/swift-argument-parser", from: "0.5.0"),
@@ -48,7 +48,8 @@ let package = Package(
       name: "_URLRouting", dependencies: ["Parsing"]
     ),
     .testTarget(
-      name: "_URLRoutingTests", dependencies: [
+      name: "_URLRoutingTests",
+      dependencies: [
         "_URLRouting",
         .product(name: "CustomDump", package: "swift-custom-dump"),
       ]

README.md

@@ -254,10 +254,6 @@ README Example.Scanner           19786.000 ns ±  35.26 %      62125
 
 That's the basics of parsing a simple string format, but there's a lot more operators and tricks to learn in order to performantly parse larger inputs. Read the [documentation][swift-parsing-docs] to dive more deeply into the concepts of parsing, and view the [benchmarks](Sources/swift-parsing-benchmark) for more examples of real life parsing scenarios.
 
-### Error messages
-
-All parsers and operators that ship with this library provide 
-
 ## Benchmarks
 
 This library comes with a benchmark executable that not only demonstrates the performance of the library, but also provides a wide variety of parsing examples: