chore(bin): rename py-update to py-dev and use repo-local Python launcher

Rename `bin/py-update`/`bin/py-update.cmd` to `bin/py-dev`/`bin/py-dev.cmd`.
Standardize both scripts to invoke the repository-local Python launcher from
the script directory (`$SCRIPT_DIR/py` / `%~dp0py.cmd`), install the project's
`requirements-dev.txt` from the repo root, and run `setup.py develop` for the
three local packages.

- Renamed: bin/py-update -> bin/py-dev (POSIX)
- Renamed: bin/py-update.cmd -> bin/py-dev.cmd (Windows)
- Scripts now: install `requirements-dev.txt` from project root and run package dev installs

Author: dimaslanjaka

bin/py-dev

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+"$SCRIPT_DIR/py" -m pip install -r "$SCRIPT_DIR/../requirements-dev.txt"
+"$SCRIPT_DIR/py" packages/proxy-hunter-python/setup.py develop
+"$SCRIPT_DIR/py" packages/proxy-checker-python/setup.py develop
+"$SCRIPT_DIR/py" packages/rsa-utility/setup.py develop

bin/py-dev.cmd

@@ -0,0 +1,6 @@
+@echo off
+
+"%~dp0py.cmd" -m pip install -r "%~dp0..\requirements-dev.txt"
+"%~dp0py.cmd" packages/proxy-hunter-python/setup.py develop
+"%~dp0py.cmd" packages/proxy-checker-python/setup.py develop
+"%~dp0py.cmd" packages/rsa-utility/setup.py develop