Add dropdown to select loader version manually

Problem Statement

Unable to select specific mod loader version when creating a server. Always selects most up to date loader which causes issues when packs use older loader version

Who will benefit?

Anyone who is running a pack that is not up to date or using mods that rely on older versions of the mod loader.

Benefits and risks

What benefits does this bring?
    - more customizable server installs
    - extend functionality
    - removes effort of manually installing correct loader version over newer version

What risks might this introduce?
    - may cause issues for users who are unsure of settings purpose and select incorrect loader version.

Proposed solution

Add option to select specific loader version to install. Perhaps have it hidden, or default to most up to date version.

Examples

A modpack currently effected by this issue is Create:Astral. Pterodactyl has the feature to manually specify the required version so all modpacks / versions are supported easily via GUI

Priority/Severity

• High (This will bring a huge increase in performance/productivity/usability)
• Medium (This will bring a good increase in performance/productivity/usability)
• Low (anything else e.g., trivial, minor improvements)