Add jwt benchmarks

.gitignore

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+*bench.exec

jwt/Makefile

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+run:
+	go test -c -o jwt-bench.exec
+	time ./jwt-bench.exec -test.v -test.benchmem -test.bench ^Benchmark -test.count 5 -test.run ^$ > bench.txt

jwt/README.md

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+# jwt
+
+## Who
+
+```
+github.com/cristalhq/jwt/v4 v4.0.0
+github.com/golang-jwt/jwt v3.2.2+incompatible
+github.com/lestrrat-go/jwx v1.2.23
+github.com/pascaldekloe/jwt v1.10.0
+```
+
+## Where
+
+```
+MacBook Pro (15-inch, 2017)
+2,8 GHz Quad-Core Intel Core i7
+16 GB 2133 MHz LPDDR3
+```
+
+## How
+
+```shell script
+# build & run benchmark
+$ make run
+
+# or in steps
+
+# build test executable
+$ go test -c -o jwt-bench.exec
+
+# run executable
+$ time ./jwt-bench.exec -v -benchmem -bench ^Benchmark -count 5 -run ^$ > bench.txt
+```
+
+## Well
+
+See [bench.txt](https://github.com/cristalhq/benchmarks/blob/main/jwt/bench.txt)