Add Loot Tables extension

[thp21000]

Adds Loot Tables to the Owlbear Rodeo extension store.

Store file:
https://raw.githubusercontent.com/thp21000/loot-tables-for-OBR/main/public/store.md

Manifest:
https://thp21000.github.io/loot-tables-for-OBR/manifest.json

Make sure that your submission has the following:

• A link to the raw github markdown file with a YAML front matter definition containing:
  • The title of your extension
  • A description of your extension
  • The author
  • A hero image
  • An icon
  • Tags (these will help with your extension's discoverability)
  • A link to your extensions manifest

Please, go through these steps before you submit a PR.

• You have done your changes in a separate branch.

• You have a descriptive commit message with a short title (first line).

• You have only one commit (if not, squash them into one commit).

• Your pull request MUST target the main branch on this repository.

• Your pull request puts your extensions details as the last entry in the extensions.json file

[Several-Record7234]

Validation script and image URLs check out fine. 'Learn-more' link is fine.

Extension functionality and API usage not checked.