Add missing properties to AlignedSegment type stubs (PR #1273)

These properties were added on the master branch during the type hints
PR's development. The PR was (understandably) not updated with these
additions before it was merged, so add them now.

pysam/libcalignedsegment.pyi

@@ -88,8 +88,12 @@ class AlignedSegment:
     is_proper_pair: bool
     is_unmapped: bool
     mate_is_unmapped: bool
+    is_mapped: bool
+    mate_is_mapped: bool
     is_reverse: bool
     mate_is_reverse: bool
+    is_forward: bool
+    mate_is_forward: bool
     is_read1: bool
     is_read2: bool
     is_secondary: bool
@@ -121,6 +125,10 @@ class AlignedSegment:
     @property
     def query_alignment_end(self) -> int: ...
     @property
+    def modified_bases(self) -> Optional[Dict[Tuple[str, int, str], List[Tuple[int, int]]]]: ...
+    @property
+    def modified_bases_forward(self) -> Optional[Dict[Tuple[str, int, str], List[Tuple[int, int]]]]: ...
+    @property
     def query_alignment_length(self) -> int: ...
     def infer_query_length(self) -> Optional[int]: ...
     def infer_read_length(self) -> Optional[int]: ...