Create a proper Pyhton packages for printer-linter

Such that it can be downloaded, installed and used locally and on other
repo's actions etc

printer-linter/src/printerlinter/meshes.py

@@ -0,0 +1,34 @@
+from .diagnostic import Diagnostic
+
+
+class Meshes:
+    def __init__(self, file, settings):
+        self._settings = settings
+        self._file = file
+        self._max_file_size = self._settings.get("diagnostic-mesh-file-size", 1e6)
+
+    def check(self):
+        if self._settings["checks"].get("diagnostic-mesh-file-extension", False):
+            for check in self.checkFileFormat():
+                yield check
+
+        if self._settings["checks"].get("diagnostic-mesh-file-size", False):
+            for check in self.checkFileSize():
+                yield check
+
+        yield
+
+    def checkFileFormat(self):
+        if self._file.suffix.lower() not in (".3mf", ".obj", ".stl"):
+            yield Diagnostic("diagnostic-mesh-file-extension",
+                             f"Extension **{self._file.suffix}** not supported, use **3mf**, **obj** or **stl**",
+                             self._file)
+        yield
+
+    def checkFileSize(self):
+
+        if self._file.stat().st_size > self._max_file_size:
+            yield Diagnostic("diagnostic-mesh-file-size",
+                             f"Mesh file with a size **{self._file.stat().st_size}** is bigger then allowed maximum of **{self._max_file_size}**",
+                             self._file)
+        yield