Repo improvements

- Improved README.md
- Added examples
- Added `session_storage/` to .gitignore so that examples do not introduce leftover files after execution

examples/_environment.py

@@ -0,0 +1,18 @@
+import os
+import sys
+
+def check_environment() -> None:
+    """
+    This function checks if required environment variables are set. It prints
+    problem resolution guide and exits using `sys.exit(1)` on problem.
+    """
+    if "MATRIX_HOMESERVER" not in os.environ:
+        print("Please set `MATRIX_HOMESERVER` environment variable!")
+        print("P.S. use something like this in your shell:")
+        print("    export MATRIX_HOMESERVER=\"https://matrix.server.net\"")
+        sys.exit(1)
+    if "MATRIX_USERNAME" not in os.environ:
+        print("Please set `MATRIX_USERNAME` environment variable!")
+        print("P.S. use something like this in your shell:")
+        print("    export MATRIX_USERNAME=\"megakiller228\"")
+        sys.exit(1)