Add Config File Parsing

[ajschmidt8]

This PR adds support for a .github/ops-bot.yaml configuration file that can be checked into each repository to enable/disable certain features of the ops-bot application. The configuration file will be in YAML format and will look like this:

# default values are shown here
auto_merger: false
branch_checker: false
label_checker: false
release_drafter: false
external_contributors: true

The format, file path, and default values are all shown in src/config.ts.

To Do:

• Add documentation to README
• Add initial ops-bot.yaml file to each repository that the ops-bot GitHub application is currently installed on
• Make ops-bot repository public?

[ajschmidt8]

PRs for public repos:

• Add .github/ops-bot.yaml config file [skip ci] cudf#10420
• Add .github/ops-bot.yaml config file [skip ci] cuml#4630
• Add .github/ops-bot.yaml config file [skip ci] cugraph#2111
• Add .github/ops-bot.yaml config file [skip ci] rmm#991
• Add .github/ops-bot.yaml config file [skip ci] cuxfilter#352
• Add .github/ops-bot.yaml config file [skip ci] dask-cuda#871
• Add .github/ops-bot.yaml config file [skip ci] clx#477
• Add .github/ops-bot.yaml config file [skip ci] raft#554
• Add .github/ops-bot.yaml config file [skip ci] cuspatial#496
• Add .github/ops-bot.yaml config file [skip ci] cusignal#463
• Add .github/ops-bot.yaml config file [skip ci] rapids-cmake#163
• Add .github/ops-bot.yaml config file [skip ci] cucim#236