Add blacklist support for contributors (#15)

* Initial plan

* Initial implementation plan for blacklist feature

Agent-Logs-Url: https://github.com/ohcnetwork/leaderboard-github-plugin/sessions/45cce8fe-c629-4318-b7bd-dd55930b6079

Co-authored-by: rithviknishad <25143503+rithviknishad@users.noreply.github.com>

* Add blacklist support for contributors

Agent-Logs-Url: https://github.com/ohcnetwork/leaderboard-github-plugin/sessions/45cce8fe-c629-4318-b7bd-dd55930b6079

Co-authored-by: rithviknishad <25143503+rithviknishad@users.noreply.github.com>

* changeset

---------

Co-authored-by: anthropic-code-agent[bot] <242468646+Claude@users.noreply.github.com>
Co-authored-by: rithviknishad <25143503+rithviknishad@users.noreply.github.com>
Co-authored-by: Rithvik Nishad <rithvikn2001@gmail.com>
Co-authored-by: rithviknishad <mail@rithviknishad.dev>

Author: Claude

.changeset/curly-lights-wear.md

@@ -0,0 +1,5 @@
+---
+"@ohcnetwork/leaderboard-github-plugin": minor
+---
+
+Adds support for blacklisting github users

README.md

@@ -20,6 +20,10 @@ leaderboard:
         #   - ${{ env.GITHUB_TOKEN_1 }}
         #   - ${{ env.GITHUB_TOKEN_2 }}
         #   - ${{ env.GITHUB_TOKEN_3 }}
+        # Optional: Blacklist contributors (exclude from tracking):
+        # blacklist:
+        #   - invalid-email-address
+        #   - bot-account
 ```
 
 ### Config Options
@@ -29,6 +33,7 @@ leaderboard:
 | `githubOrg` | `string` | Yes | GitHub organization name |
 | `githubToken` | `string` | Yes* | A single GitHub personal access token |
 | `githubTokens` | `string[]` | Yes* | Array of GitHub tokens for rotation on rate limit |
+| `blacklist` | `string[]` | No | Array of GitHub usernames to exclude from tracking |
 
 \* At least one of `githubToken` or `githubTokens` must be provided. When multiple tokens are supplied, the plugin automatically rotates to the next available token when one hits GitHub's rate limit, instead of waiting an hour.