support IS_SENT_START in PhraseMatcher (#6771)

* support IS_SENT_START in PhraseMatcher

* add unit test and friendlier error

* use IDS.get instead

spacy/matcher/phrasematcher.pyx

@@ -8,6 +8,7 @@ from preshed.maps cimport map_init, map_set, map_get, map_clear, map_iter
 
 import warnings
 
+from ..attrs import IDS
 from ..attrs cimport ORTH, POS, TAG, DEP, LEMMA
 from ..structs cimport TokenC
 from ..tokens.token cimport Token
@@ -58,9 +59,11 @@ cdef class PhraseMatcher:
             attr = attr.upper()
             if attr == "TEXT":
                 attr = "ORTH"
+            if attr == "IS_SENT_START":
+                attr = "SENT_START"
             if attr not in TOKEN_PATTERN_SCHEMA["items"]["properties"]:
                 raise ValueError(Errors.E152.format(attr=attr))
-            self.attr = self.vocab.strings[attr]
+            self.attr = IDS.get(attr)
 
     def __len__(self):
         """Get the number of match IDs added to the matcher.

spacy/tests/matcher/test_phrase_matcher.py

@@ -290,3 +290,8 @@ def test_phrase_matcher_pickle(en_vocab):
     # clunky way to vaguely check that callback is unpickled
     (vocab, docs, callbacks, attr) = matcher_unpickled.__reduce__()[1]
     assert isinstance(callbacks.get("TEST2"), Mock)
+
+
+@pytest.mark.parametrize("attr", ["SENT_START", "IS_SENT_START"])
+def test_phrase_matcher_sent_start(en_vocab, attr):
+    matcher = PhraseMatcher(en_vocab, attr=attr)