Support Buf Schema Registry

[k1LoW]

ref: https://buf.build/docs/bsr/introduction

[github-actions]

Code Metrics Report

	main (b287f5b)	#77 (7a1884c)	+/-
Coverage	82.0%	81.5%	-0.5%
Code to Test Ratio	1:0.4	1:0.4	-0.0

Details

  |                    | main (b287f5b) | #77 (7a1884c) |  +/-  |
  |--------------------|----------------|---------------|-------|
- | Coverage           |          82.0% |         81.5% | -0.5% |
  |   Files            |              3 |             3 |     0 |
  |   Lines            |            650 |           670 |   +20 |
+ |   Covered          |            533 |           546 |   +13 |
- | Code to Test Ratio |          1:0.4 |         1:0.4 |  -0.0 |
  |   Code             |           2163 |          2464 |  +301 |
  |   Test             |            883 |           883 |     0 |

Code coverage of files in pull request scope (81.6% → 81.0%)

Files	Coverage	+/-
grpcstub.go	83.2%	+0.2%
option.go	62.5%	-4.8%

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Reported by octocov