feature: added a pest_debugger crate (fixes #98)

based on the old PR by @dragostis: #277

Changes that were made:
- debugger core context was refactored and extracted to a lib (so that
it could be used in other frontends, e.g. editor plugins)
- CLI was extended using rustyline helpers to provide file completions,
history etc.
- applied suggestions from @hansihe from the old PR
(#277 (comment)):
1. added `ba` (add breakpoints at all rules) which is useful
for stepping through the entire grammar, plus breakpoint deletions
and loading input directly from readline;
2. added command line arguments.
- changed the listener function to return a boolean, so that
the debugger can signal back to a parsing thread to finish
before reaching its input's EOF.

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = [
     "bootstrap",
+    "debugger",
     "derive",
     "generator",
     "grammars",

debugger/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "pest_debugger"
+description = "pest grammar debugger"
+version = "2.5.0"
+edition = "2021"
+authors = ["Dragoș Tiselice <dragostiselice@gmail.com>", "Tomas Tauber <me@tomtau.be>"]
+homepage = "https://pest.rs/"
+repository = "https://github.com/pest-parser/pest"
+documentation = "https://docs.rs/pest"
+keywords = ["pest", "grammar", "debugger"]
+categories = ["parsing"]
+license = "MIT/Apache-2.0"
+readme = "_README.md"
+rust-version = "1.56"
+
+[dependencies]
+pest = { path = "../pest", version = "2.5.0" }
+pest_meta = { path = "../meta", version = "2.5.0" }
+pest_vm = { path = "../vm", version = "2.5.0" }
+rustyline = "10"
+thiserror = "1"
+
+[badges]
+codecov = { repository = "pest-parser/pest" }
+maintenance = { status = "actively-developed" }
+github = { repository = "pest-parser/pest" }

debugger/_README.md

@@ -0,0 +1 @@
+../README.md