Add mdbook-preprocessor and mdbook-renderer

These are two new crates intended to support implementing preprocessors
and renderers. Currently these stubs just have MDBOOK_VERSION, but
future commits will migrate more code to these crates.

Cargo.lock

@@ -1298,6 +1298,13 @@ dependencies = [
 name = "mdbook-core"
 version = "0.5.0-alpha.1"
 
+[[package]]
+name = "mdbook-preprocessor"
+version = "0.5.0-alpha.1"
+dependencies = [
+ "mdbook-core",
+]
+
 [[package]]
 name = "mdbook-remove-emphasis"
 version = "0.1.0"
@@ -1308,6 +1315,13 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "mdbook-renderer"
+version = "0.5.0-alpha.1"
+dependencies = [
+ "mdbook-core",
+]
+
 [[package]]
 name = "memchr"
 version = "2.7.5"

crates/mdbook-preprocessor/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "mdbook-preprocessor"
+version = "0.5.0-alpha.1"
+description = "Library to assist implementing an mdBook preprocessor"
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+mdbook-core.workspace = true
+
+[lints]
+workspace = true

crates/mdbook-preprocessor/src/lib.rs

@@ -0,0 +1,3 @@
+//! Library to assist implementing an mdbook preprocessor.
+
+pub use mdbook_core::MDBOOK_VERSION;

crates/mdbook-renderer/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "mdbook-renderer"
+version = "0.5.0-alpha.1"
+description = "Library to assist implementing an mdBook renderer"
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+mdbook-core.workspace = true
+
+[lints]
+workspace = true

crates/mdbook-renderer/src/lib.rs

@@ -0,0 +1,3 @@
+//! Library to assist implementing an mdbook renderer.
+
+pub use mdbook_core::MDBOOK_VERSION;