Add optional dependencies support via extras_require

- Create requirements-core.txt with only core dependencies (requests, dateparser)
- Update setup.py to support extras_require with 'dataframe', 'numpy', 'plot', and 'all' options
- Update README.md with installation instructions for optional dependencies
- Users can now install minimal version without pandas/matplotlib/numpy for reduced memory footprint

Co-authored-by: 4n4nd <22333506+4n4nd@users.noreply.github.com>

Author: Copilot

README.md

@@ -11,6 +11,18 @@ To install the latest release:
 
 `pip install prometheus-api-client`
 
+To install with all optional dependencies (pandas, numpy, matplotlib):
+
+`pip install prometheus-api-client[all]`
+
+**Note:** Starting from version 0.6.0, pandas, numpy, and matplotlib are optional dependencies. 
+If you only need `PrometheusConnect` without DataFrame support or plotting capabilities, you can install the minimal version which significantly reduces memory footprint and installation time, especially on Alpine-based Docker images.
+
+To install only specific extras:
+- For DataFrame support: `pip install prometheus-api-client[dataframe]`
+- For numpy support: `pip install prometheus-api-client[numpy]`
+- For plotting support: `pip install prometheus-api-client[plot]`
+
 To install directly from this branch:
 
 `pip install https://github.com/4n4nd/prometheus-api-client-python/zipball/master`

requirements-core.txt

@@ -0,0 +1,2 @@
+requests
+dateparser

setup.py

@@ -7,8 +7,8 @@
 
 
 def get_install_requires():
-    """Get requirements from requirements.txt."""
-    with open("requirements.txt", "r") as requirements_file:
+    """Get core requirements from requirements-core.txt."""
+    with open("requirements-core.txt", "r") as requirements_file:
         res = requirements_file.readlines()
         return [req.split(" ", maxsplit=1)[0] for req in res if req]
 
@@ -36,6 +36,12 @@ def get_version():
     long_description_content_type="text/markdown",
     url="https://github.com/4n4nd/prometheus-api-client-python",
     install_requires=get_install_requires(),
+    extras_require={
+        "dataframe": ["pandas>=1.4.0"],
+        "numpy": ["numpy"],
+        "plot": ["matplotlib"],
+        "all": ["pandas>=1.4.0", "numpy", "matplotlib"],
+    },
     packages=setuptools.find_packages(),
     package_data={"prometheus-api-client": ["py.typed"]},
     tests_require=["httmock"],