Add syntax-highlighted source pages for GitHub Pages (#4)

Raw .java files are served as plain text by GitHub Pages, so the
Implementation links rendered without highlighting. Each source file now
has a companion <Name>.java.md wrapper that pulls the code into a
fenced java block via include_relative, which Rouge highlights in the
Cayman theme. README and docs links now target the wrapper pages;
jekyll-relative-links converts them to .html on the published site.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: williajm

docs/anti-patterns.md

@@ -36,7 +36,7 @@ business rule is unfindable and unsearchable; when "free shipping over GBP 25" b
 the 25.00s get updated (see [copy-paste programming](#3-copy-paste-programming)); `status == 3`
 invites off-by-one bugs no compiler can catch. **The counter:** named constants
 (`FREE_SHIPPING_THRESHOLD`) and enums --
-[`PaymentMethod`](../src/main/java/com/bookshop/creational/factorymethod/PaymentMethod.java) makes
+[`PaymentMethod`](../src/main/java/com/bookshop/creational/factorymethod/PaymentMethod.java.md) makes
 invalid payment types unrepresentable, and the compiler checks every `switch` over it.
 
 ## 3. Copy-paste programming

src/main/java/com/bookshop/behavioral/chainofresponsibility/AddressCheck.java.md

@@ -0,0 +1,9 @@
+---
+title: AddressCheck.java
+---
+
+```java
+{% include_relative AddressCheck.java %}
+```
+
+[Raw file](AddressCheck.java)

src/main/java/com/bookshop/behavioral/chainofresponsibility/FraudCheck.java.md

@@ -0,0 +1,9 @@
+---
+title: FraudCheck.java
+---
+
+```java
+{% include_relative FraudCheck.java %}
+```
+
+[Raw file](FraudCheck.java)

src/main/java/com/bookshop/behavioral/chainofresponsibility/OrderCheck.java.md

@@ -0,0 +1,9 @@
+---
+title: OrderCheck.java
+---
+
+```java
+{% include_relative OrderCheck.java %}
+```
+
+[Raw file](OrderCheck.java)

src/main/java/com/bookshop/behavioral/chainofresponsibility/OrderRequest.java.md

@@ -0,0 +1,9 @@
+---
+title: OrderRequest.java
+---
+
+```java
+{% include_relative OrderRequest.java %}
+```
+
+[Raw file](OrderRequest.java)

src/main/java/com/bookshop/behavioral/chainofresponsibility/README.md

@@ -37,12 +37,12 @@ Servlet `Filter` chains, Spring Security's filter chain, Spring MVC interceptors
 
 ## Implementation
 
-- [`OrderCheck`](OrderCheck.java) -- the handler interface, including the chain assembly.
-- [`StockCheck`](StockCheck.java), [`AddressCheck`](AddressCheck.java),
-  [`FraudCheck`](FraudCheck.java) -- the concrete checks.
-- [`OrderRequest`](OrderRequest.java), [`ValidationResult`](ValidationResult.java) -- the request
+- [`OrderCheck`](OrderCheck.java.md) -- the handler interface, including the chain assembly.
+- [`StockCheck`](StockCheck.java.md), [`AddressCheck`](AddressCheck.java.md),
+  [`FraudCheck`](FraudCheck.java.md) -- the concrete checks.
+- [`OrderRequest`](OrderRequest.java.md), [`ValidationResult`](ValidationResult.java.md) -- the request
   and result types.
 
 ## Example test
 
-[`OrderValidationChainTest`](../../../../../../test/java/com/bookshop/behavioral/chainofresponsibility/OrderValidationChainTest.java)
+[`OrderValidationChainTest`](../../../../../../test/java/com/bookshop/behavioral/chainofresponsibility/OrderValidationChainTest.java.md)

src/main/java/com/bookshop/behavioral/chainofresponsibility/StockCheck.java.md

@@ -0,0 +1,9 @@
+---
+title: StockCheck.java
+---
+
+```java
+{% include_relative StockCheck.java %}
+```
+
+[Raw file](StockCheck.java)

src/main/java/com/bookshop/behavioral/chainofresponsibility/ValidationResult.java.md

@@ -0,0 +1,9 @@
+---
+title: ValidationResult.java
+---
+
+```java
+{% include_relative ValidationResult.java %}
+```
+
+[Raw file](ValidationResult.java)

src/main/java/com/bookshop/behavioral/observer/EmailAlerts.java.md

@@ -0,0 +1,9 @@
+---
+title: EmailAlerts.java
+---
+
+```java
+{% include_relative EmailAlerts.java %}
+```
+
+[Raw file](EmailAlerts.java)

src/main/java/com/bookshop/behavioral/observer/Inventory.java.md

@@ -0,0 +1,9 @@
+---
+title: Inventory.java
+---
+
+```java
+{% include_relative Inventory.java %}
+```
+
+[Raw file](Inventory.java)