Find appropriate URL for given forge version

[the-be-to]

The URL for the Forge download is currently assumed to be in the form of '.../forge/%s/forge-%s-installer.jar' % (forge_fullver, forge_fullver), but upon inspecting various versions, there is a greater variety. e.g
Minecraft 1.7.10, Forge 10.13.4.1614: .../forge/1.7.10-10.13.4.1614-1.7.10/forge-1.7.10-10.13.4.1614-1.7.10-installer.jar
Minecraft 1.7.10, Forge 10.13.3.1395: .../forge/1.7.10-10.13.3.1395-1710ls/forge-1.7.10-10.13.3.1395-1710ls-installer.jar
A function get_forge_url() was implemented to obtain the required download URL by scraping the Forge download page for the specified Minecraft version, and using a regex to find the appropriate URL for the specified Forge version.
The following shows its use:

Python 3.10.9 (main, Dec 25 2022, 21:29:15) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from forge_install import get_forge_url
>>> get_forge_url("1.7.10", "10.13.4.1614")
Downloading https://files.minecraftforge.net/net/minecraftforge/forge/index_1.7.10.html
'https://maven.minecraftforge.net/net/minecraftforge/forge/1.7.10-10.13.4.1614-1.7.10/forge-1.7.10-10.13.4.1614-1.7.10-installer.jar'
>>> get_forge_url("1.7.10", "10.13.3.1395")
'https://maven.minecraftforge.net/net/minecraftforge/forge/1.7.10-10.13.3.1395-1710ls/forge-1.7.10-10.13.3.1395-1710ls-installer.jar'
>>> get_forge_url("1.12.2", "14.23.5.2860")
Downloading https://files.minecraftforge.net/net/minecraftforge/forge/index_1.12.2.html
'https://maven.minecraftforge.net/net/minecraftforge/forge/1.12.2-14.23.5.2860/forge-1.12.2-14.23.5.2860-installer.jar'

This resolves the issue noted in #16.

[cdbbnnyCode]

Looks good; I'd suggest adding a fallback in case the HTML scraper fails, since the default pattern still applies for most versions.