GitHub Occurrences Badge

:clipboard: **Description**

A badge for GitHub that counts the occurrences of a sequence in a file.

For example, given `/github/occurances/badges/shields/README.md/badge`, the badge would show *22* (badge occurs in README.md 22 times).

Optimally, sequence should be a regular expression (escape sequences, word boundaries, character classes).

:link: **Data**

The data required for this can be retrieved from `https://raw.githubusercontent.com/:user/:repo/:branch/:path`. It only requires authentication for private repositories.
Unfortunately I don't know of any official documentation for this endpoint, only that it is the destination when pressing "Raw" on a file on GitHub.

Additional processing is required and would need to be limited.

:microphone: **Motivation**

I personally want to use it to count the number of facts in a text file (each fact is on its own line).
A badge for counting lines would work, but being able to count anything opens the door for a lot more opportunity:
- How many times is "as you know" mentioned in a story?
- How many times, if at all, is `goto` used?
- How many code blocks are present?
- How many references to a shutdown API exist?

Start by reviewing the proposed raw.githubusercontent.com URL and the example GitHub occurrence badge path; the issue does not name repository files or tests. Define the supported sequence or regular-expression input, processing limits, and private-repository behavior, then verify that the resulting badge reports the expected occurrence count.

Written by the indexing model from the issue text.