[Feature] Add svtr encoder (#1483)

* add svtr backbone

* update backbone

* fix

* apply comments, move backbone to encoder

Co-authored-by: gaotongxiao <[email protected]>

Author: willpat1213

mmocr/models/textrecog/encoders/__init__.py

@@ -6,8 +6,9 @@
 from .nrtr_encoder import NRTREncoder
 from .sar_encoder import SAREncoder
 from .satrn_encoder import SATRNEncoder
+from .svtr_encoder import SVTREncoder
 
 __all__ = [
     'SAREncoder', 'NRTREncoder', 'BaseEncoder', 'ChannelReductionEncoder',
-    'SATRNEncoder', 'ABIEncoder', 'ASTEREncoder'
+    'SATRNEncoder', 'ABIEncoder', 'SVTREncoder', 'ASTEREncoder'
 ]