You can easily extract all your //TODOs with grep:
grep TODO -rnf * > TODOs.txt
Then it should be possible to write a small script that reads this TODOs.txt file and makes use of Github's api to create new issues:
POST /repos/:owner/:repo/issues
{
"title": "Found a bug",
"body": "I'm having a problem with this.",
"assignee": "octocat",
"milestone": 1,
"labels": [
"Label1",
"Label2"
]
}
But this is left as an exercise ;)