GP-0: Certify and README update

Ghidra/Features/PyGhidra/certification.manifest

@@ -17,3 +17,4 @@ src/main/py/LICENSE||GHIDRA||||END|
 src/main/py/MANIFEST.in||GHIDRA||||END|
 src/main/py/README.md||GHIDRA||||END|
 src/main/py/pyproject.toml||GHIDRA||||END|
+src/main/py/src/pyghidra/py.typed||GHIDRA||||END|

Ghidra/Features/PyGhidra/src/main/py/README.md

@@ -575,6 +575,9 @@ __3.1.0__
   `support/launch.properties` file.
 * `ghidra_launch.py` now correctly prioritizes user-defined JVM properties higher than those defined
   in `support/launch.properties`.
+* PyGhidra now includes a 
+  [`py.typed`](https://typing.python.org/en/latest/spec/distributing.html#packaging-type-information)
+  marker file to inform type checkers that typing is supported.
 
 __3.0.2__
 * Fixed an issue that prevented [`pyghidra.analysis_properties()`](#pyghidraanalysis_properties)