Add support for dynamic configuration

[DrSensor]

Fix #12

[mre]

First impression: looks good!

[DrSensor]

Alright, I will settle with this for now 👍 (feel free to merge it)

I leave it here just for future references

I have tried to create another builder pattern in another project but it seems I can't get it applied in here. I use trait and and dynamic dispatch to get it works. Here is how I do it: 1. [Define the config field](https://github.com/DrSensor/scdlang/blob/15d1c6652f69e0dd86628cba1f2db6384740a779/packages/core/src/core/builder.rs#L30-L36) ```rust pub struct Scdlang<'g> { pub(crate) path: Option<&'g str>, pub(crate) line: Option, pub(super) clear_cache: bool, //-|in case for program that need to disable…| pub(super) semantic_error: bool, //-|…then enable semantic error at runtime| } ``` 2. [Define the `Builder` trait](https://github.com/DrSensor/scdlang/blob/15d1c6652f69e0dd86628cba1f2db6384740a779/packages/core/src/external.rs#L97-L111) ```rust pub trait Builder<'t> { /** Automatically clear cache when out of scope. * `default` - set `false` to disable it. (default: `true`) The cache is used for analyzing semantics error. This can be handy when parsing in streaming fashion. */ fn auto_clear_cache(&mut self, default: bool) -> &mut dyn Builder<'t>; /// Enable semantics error. (default: `true`). fn with_err_semantic(&mut self, default: bool) -> &mut dyn Builder<'t>; /// Set path that going to be printed in the error essages. fn with_err_path(&mut self, path: &'t str) -> &mut dyn Builder<'t>; /// Set the line_of_code offset of the error essages. fn with_err_line(&mut self, line: usize) -> &mut dyn Builder<'t>; } ``` 3. [Implement the `Builder` trait](https://github.com/DrSensor/scdlang/blob/15d1c6652f69e0dd86628cba1f2db6384740a779/packages/core/src/core/builder.rs#L60-L80) ```rust impl<'g> Builder<'g> for Scdlang<'g> { fn with_err_path(&mut self, path: &'g str) -> &mut dyn Builder<'g> { self.path = Some(path); self } fn with_err_line(&mut self, line: usize) -> &mut dyn Builder<'g> { self.line = Some(line); self } fn with_err_semantic(&mut self, default: bool) -> &mut dyn Builder<'g> { self.semantic_error = default; self } fn auto_clear_cache(&mut self, default: bool) -> &mut dyn Builder<'g> { self.clear_cache = default; self } } ``` 4. [dynamic dispatch](https://github.com/DrSensor/scdlang/blob/15d1c6652f69e0dd86628cba1f2db6384740a779/packages/core/src/external.rs#L81) ```rust fn configure(&mut self) -> &mut dyn Builder<'t>; ``` 5. [make struct that implement `Builder` trait as a _member_ of another struct](https://github.com/DrSensor/scdlang/blob/15d1c6652f69e0dd86628cba1f2db6384740a779/packages/transpiler/xstate/src/asg/mod.rs#L24-L31) ```rust pub struct Machine<'a> { #[serde(skip)] builder: Scdlang<'a>, #[serde(flatten)] schema: StateChart, // TODO: replace with 👇 when https://github.com/serde-rs/serde/issues/1507 resolved // schema: mem::ManuallyDrop, } ``` 6. [Implement `configure` function in struct that have `Builder` trait as a member](https://github.com/DrSensor/scdlang/blob/15d1c6652f69e0dd86628cba1f2db6384740a779/packages/transpiler/xstate/src/asg/mod.rs#L34-L36) ```rust fn configure(&mut self) -> &mut Builder<'a> { &mut self.builder } ```