Exclude unnecessary folders from the VSIX file

[rcjsuen]

Problem Description

1. .github workflows do not need to be included in the VSIX build.
2. README.md images are loaded from GitHub so they also do not need to be included in the VSIX build.

See #30.

Proposed Solution

Added the two aforementioned folders to .vscodeignore.

Proof of Work

I ran vsce package with and without the command verified that the change works.

 INFO  Files included in the VSIX:
docker-0.1.1.vsix
├─ [Content_Types].xml
├─ extension.vsixmanifest
└─ extension/
   ├─ Dockerfile [0.43 KB]
   ├─ LICENSE.txt [10.51 KB]
   ├─ SECURITY.md [1.82 KB]
   ├─ TELEMETRY.md [1.34 KB]
   ├─ changelog.md [0.48 KB]
   ├─ docker-compose.yml [0.37 KB]
   ├─ frontend.Dockerfile [0.02 KB]
   ├─ notes.md [0.52 KB]
   ├─ package.json [3.7 KB]
   ├─ readme.md [4.83 KB]
   ├─ tmp.js [0.72 KB]
   ├─ bin/
   │  ├─ docker-language-server-darwin-arm64 [39.69 MB]
   │  └─ docker-language-server-linux-arm64 [38.36 MB]
   ├─ dist/
   │  ├─ 1.extension.js [21.23 KB]
   │  ├─ 770.extension.js [20.65 KB]
   │  └─ extension.js [349.74 KB]
   └─ resources/
      └─ docker-logo-vertical-blue.png [244.23 KB]