Add tool-alias.yml to Index Repository

[keshav-space]

The tool-alias.yml file should contain the mapping of alias to the purl for the corresponding tool. These alias are used for naming the output generated by these tools. For example, the package scan from scancode.io is named scancodeio.json.

tool-alias.yml would look like this:

tools:
  scancodeio: pkg:github/scancode.io
  scancode-toolkit: pkg:github/scancode-toolkit