Add errorstrings analyzer

[k1LoW]

ref: https://github.com/golang/go/wiki/CodeReviewComments#error-strings

[github-actions]

Code Metrics Report

	main (1d6e5cc)	#71 (b71279e)	+/-
Coverage	69.1%	69.6%	+0.5%
Code to Test Ratio	1:0.1	1:0.1	+0.0
Test Execution Time	16s	14s	-2s

Details

  |                     | main (1d6e5cc) | #71 (b71279e) |  +/-  |
  |---------------------|----------------|---------------|-------|
+ | Coverage            |          69.1% |         69.6% | +0.5% |
  |   Files             |             16 |            17 |    +1 |
  |   Lines             |            878 |           925 |   +47 |
+ |   Covered           |            607 |           644 |   +37 |
+ | Code to Test Ratio  |          1:0.1 |         1:0.1 |  +0.0 |
  |   Code              |           2694 |          2829 |  +135 |
+ |   Test              |            197 |           207 |   +10 |
+ | Test Execution Time |            16s |           14s |   -2s |

Code coverage of files in pull request scope (0.0% → 46.8%)

Files	Coverage	+/-
analyzer/code_review_comments/errorstrings/errorstrings.go	78.7%	+78.7%
config/config.go	0.0%	0.0%

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Reported by octocov