Modify CODEOWNERS

Author: lysnikolaou

.github/CODEOWNERS

@@ -316,3 +316,13 @@ Lib/test/test__colorize.py    @hugovk
 
 # Fuzzing
 Modules/_xxtestfuzz/          @ammaraskar
+
+# t-strings
+Include/internal/pycore_interpolation.h  @lysnikolaou
+Include/internal/pycore_template.h  @lysnikolaou
+Objects/interpolationobject.c  @lysnikolaou
+Objects/clinic/interpolationobject.c.h  @lysnikolaou
+Objects/templateobject.c      @lysnikolaou
+Modules/_templatelibmodule.c  @lysnikolaou
+Lib/string/templatelib.py     @lysnikolaou
+Lib/test/test_tstring.py      @lysnikolaou