MAINT: Use new PEP8 compliant names

.github/ISSUE_TEMPLATE/feature-request.md

@@ -15,7 +15,7 @@ Explain briefly what you want to achive.
 How would your feature be used? (Remove this if it is not applicable.)
 
 ```python
-from PyPDF2 import PdfFileReader, PdfFileWriter
+from PyPDF2 import PdfReader, PdfWriter
 
 ...  # your new feature in action!
 ```

PyPDF2/__init__.py

@@ -1,18 +1,22 @@
-from ._merger import PdfFileMerger
+from ._merger import PdfMerger
 from ._page import Transformation
-from ._reader import PdfFileReader
+from ._reader import DocumentInformation, PdfFileReader, PdfReader
 from ._version import __version__
-from ._writer import PdfFileWriter
+from ._writer import PdfFileWriter, PdfWriter
 from .pagerange import PageRange, parse_filename_page_ranges
 from .papersizes import PaperSize
 
 __all__ = [
     "__version__",
     "PageRange",
     "PaperSize",
+    "DocumentInformation",
     "parse_filename_page_ranges",
+    "PdfFileMerger",  # will be removed soon; use PdfMerger instead
+    "PdfFileReader",  # will be removed soon; use PdfReader instead
+    "PdfFileWriter",  # will be removed soon; use PdfWriter instead
+    "PdfMerger",
     "Transformation",
-    "PdfFileMerger",
-    "PdfFileReader",
-    "PdfFileWriter",
+    "PdfReader",
+    "PdfWriter",
 ]