docs: add Replacements-stripping recipe + example for digit false positives

Cargo.toml

@@ -37,6 +37,11 @@ name = "add_profanity"
 path = "src/add_profanity.rs"
 required-features = ["regex"]
 
+[[example]]
+name = "leetspeak_replacements"
+path = "examples/leetspeak_replacements.rs"
+required-features = ["customize"]
+
 [features]
 default = ["censor", "context"]
 censor = ["arrayvec", "bitflags", "lazy_static", "itertools", "unicode-normalization", "rustc-hash"]

README.md

@@ -132,6 +132,27 @@ If you want to add custom profanities or safe words, enable the `customize` feat
 }
 ```
 
+Digit-heavy text, like zip codes, can cause false positives via digit-to-letter substitutions (e.g. `9` → `g`, `0` → `o`). Zip codes obviously aren't a censor target, but got hit in practice in a chat bot's gas price feature which included zip code lookup. You can remove specific mappings from the default `Replacements` table:
+
+
+```rust
+#[cfg(feature = "customize")]
+{
+    use rustrict::Replacements;
+
+    // SAFETY: call once, synchronously, before any concurrent access to censoring
+    // (e.g. at startup, before spawning any tasks that censor text).
+    unsafe {
+        let replacements = Replacements::customize_default();
+        replacements.remove('9', 'g');
+        replacements.remove('0', 'o');
+        // ...repeat for any substitution causing false positives in your use-case.
+    }
+}
+```
+
+See [`examples/leetspeak_replacements.rs`](examples/leetspeak_replacements.rs) for a runnable version.
+
 If your use-case is chat moderation, and you store data on a per-user basis, you can use `rustrict::Context` as a reference implementation:
 
 ```rust

examples/leetspeak_replacements.rs

@@ -0,0 +1,22 @@
+//! Demonstrates removing specific digit/letter substitutions from the default
+//! `Replacements` table. Useful when digit-heavy text (zip codes, numeric IDs,
+//! prices, etc.) is decoding into flagged words via leetspeak-style
+//! substitutions (e.g. `9` -> `g`, `0` -> `o`) that don't apply to your use-case.
+//!
+//! Run with: `cargo run --example leetspeak_replacements --features customize`
+
+use rustrict::Replacements;
+
+fn main() {
+    // SAFETY: call once, synchronously, before any concurrent access to censoring
+    // (e.g. at startup, before spawning any tasks that censor text).
+    unsafe {
+        let replacements = Replacements::customize_default();
+        replacements.remove('9', 'g');
+        replacements.remove('0', 'o');
+        // ...repeat for any substitution causing false positives in your use-case.
+    }
+
+    // Digits still match themselves; only the letter interpretations are removed.
+    println!("Replacements customized; '9' no longer maps to 'g', '0' no longer maps to 'o'.");
+}