Added Subreddit data structure and search of /r/subreddit/about endpoint

...Data Collection/Pushshift API/ReadRedditCommentFile.swift

.../1. Data Collection/Pushshift API/RedditCommentData.swift

...LP/1. Data Collection/Pushshift API/RedditContainer.swift

... Data Collection/Pushshift API/RedditSubmissionData.swift

...a Collection/Pushshift API/readRedditSubmissionData.swift

...LP/1. Data Collection/Reddit API/Data Types/Comment.swift

... Collection/Reddit API/Data Types/Listing + Codable.swift

...LP/1. Data Collection/Reddit API/Data Types/Listing.swift

...1. Data Collection/Reddit API/Data Types/Submission.swift

.../1. Data Collection/Reddit API/Data Types/Subreddit.swift

...it API/Network Endpoints/Session + Subreddit Search.swift

...lection/Reddit API/Network Endpoints/Session + _GET.swift

Sources/SwiftNLP/1. Data Collection/Reddit API/Session.swift

Tests/SwiftNLPTests/Reddit API/Session Tests.swift