Build khoj python package using hatchling, pyproject.toml

- Why
  - pyprojects.toml is the python standards compliant config format
    - allows collating python tooling configs into single standard file
  - hatch(-ling) is a new lightweight build system for python packages

- Detailed Changes
  - Replace setup.py, setuptools with pyproject.toml, hatchling for
    khoj python config and build
  - move pytest into optional development dependencies
  - add more links to khoj in the project urls section
  - add topic classifiers and keywords to find khoj package

  - Delete setup.py, MANIFEST.in as moved to pyproject.toml based setup
  - Update pypi workflow to set python package version in pyproject.toml

pyproject.toml

@@ -0,0 +1,76 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "khoj-assistant"
+version = "0.3.0"
+description = "A natural language search engine for your personal notes, transactions and images"
+readme = "README.md"
+license = "GPL-3.0-or-later"
+requires-python = ">=3.8, <3.11"
+authors = [
+    { name = "Debanjum Singh Solanky", email = "debanjum+pypi@gmail.com" },
+    { name = "Saba Imran", email = "narmiabas@gmail.com" },
+]
+keywords = [
+    "search",
+    "semantic-search",
+    "productivity",
+    "NLP",
+    "AI",
+    "org-mode",
+    "markdown",
+    "beancount",
+    "images",
+]
+classifiers = [
+    "Development Status :: 4 - Beta",
+    "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
+    "Topic :: Internet :: WWW/HTTP :: Indexing/Search",
+    "Topic :: Scientific/Engineering :: Artificial Intelligence",
+    "Topic :: Scientific/Engineering :: Human Machine Interfaces",
+    "Topic :: Text Processing :: Linguistic",
+]
+dependencies = [
+    "dateparser == 1.1.1",
+    "defusedxml == 0.7.1",
+    "fastapi == 0.77.1",
+    "jinja2 == 3.1.2",
+    "openai == 0.20.0",
+    "pillow == 9.3.0",
+    "pydantic == 1.9.1",
+    "pyqt6 == 6.3.1",
+    "pyyaml == 6.0",
+    "rich >= 13.3.1",
+    "schedule == 1.1.0",
+    "sentence-transformers == 2.2.2",
+    "torch == 1.13.1",
+    "uvicorn == 0.17.6",
+]
+
+[project.urls]
+Homepage = "https://github.com/debanjum/khoj"
+Issues = "https://github.com/debanjum/khoj/issues"
+Discussions = "https://github.com/debanjum/khoj/discussions"
+Releases = "https://github.com/debanjum/khoj/releases"
+
+[project.scripts]
+khoj = "khoj.main:run"
+
+[project.optional-dependencies]
+test = [
+  "pytest == 7.1.2",
+]
+dev = ["khoj-assistant[test]"]
+
+[tool.hatch.build.targets.sdist]
+include = ["src/khoj"]
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/khoj"]