fix: infinite loop when using .* patterns

Summary:

When we are using `.*` patterns, this causes an infinite loop. What happens is
we are adding text to the end and then replacing that. Its only when we are
matching the end of the output string.

We can detect this when the starting point is the same as the end point and the
match is "" (an empty string). If we hit this condition we can get out and
return the output that has been replaced.

Test Plan:

Test in CI

src/lib.rs

@@ -26,6 +26,12 @@ pub fn replace(search: &String, replace: String, input: String) -> String {
         let start = search_match.start();
         let end = search_match.end();
 
+        // Prevent an infinite loop. If we hit this condition we will keep adding a new replacement
+        // to the end.
+        if start == end {
+            break;
+        }
+
         let mut replacement = String::new();
         match search_pattern.captures(&output[start..end]) {
             Some(captures) => {

tests/features/regex.feature

@@ -22,4 +22,16 @@ Feature: Regex search and replace
     Given Search is '(\w+'
     And Replace is 'new'
     And Input is 'this is a'
-    Then Output is 'this is a' 
+    Then Output is 'this is a'
+
+  Scenario: You can replace a pattern with a dot in it like a css class name
+    Given Search is '.testing'
+    And Replace is '.another'
+    And Input is '.testing {'
+    Then Output is '.another {'
+
+  Scenario: You can replace a pattern that grabs all the text
+    Given Search is '.*'
+    And Replace is '.another'
+    And Input is '.testing {'
+    Then Output is '.another'