Add Dockerfile and File-based Caching (Self-Hosted)

[ironashram]

This PR adds Dockerfile and a simple file based caching mechanism, i've been battling slowness and timeouts for a very long time while using this project in my gh profile and this has made a huge impact.

In my testing i've gone from around 4s for each request to under 100ms (after the first one gets cached obviously)
This is currently deployed and used in my own profile with a self hosted Coolify instance.

For the Dockerfile i used node:lts-alpine, this was inspired from another PR that was already opened in the past, includes a health check, and exposes a configurable port via the PORT environment variable (defaults to 9000).

File-based caching system is defined in a new module (src/common/fileCache.js) that persists API responses to disk, reducing GitHub API calls significantly. The cache uses a 24-hour TTL by default, generates unique keys via MD5 hashes of request parameters, and handles errors gracefully so caching failures never break actual requests.

Integrated caching into all data fetchers:

• stats.js
• top-languages.js
• repo.js
• gist.js
• wakatime.js

This is extremely beneficial in selfhosted docker scenario, i am not sure it would make any difference in Vercel since storage may not be persistent, anyway it should not break that kind of deployment or have any impact.

[vercel]

@ironashram is attempting to deploy a commit to the github readme stats Team on Vercel.

A member of the Team first needs to authorize it.