add benchmarks for simple serialization cases

[Mpdreamz]

Every library needs a BenchmarkDotNet project so this was long overdue.

Looking to get this in so we can set a base line for the changes in #75 cc @snakefoot

Method	Mean	Error	StdDev	Completed Work Items	Lock Contentions	Gen 0	Gen 1	Gen 2	Allocated
Empty	849.1 ns	3.22 ns	2.51 ns	0.0000	-	0.1135	-	-	712 B
Minimal	1,441.0 ns	13.18 ns	11.69 ns	0.0000	-	0.1469	-	-	928 B
Complex	3,913.2 ns	50.75 ns	44.99 ns	0.0000	-	0.3357	-	-	2152 B
Full	167,661.3 ns	1,491.39 ns	1,322.08 ns	0.0005	-	6.5918	0.7324	-	42194 B

[apmmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #81 updated]

• Start Time: 2020-06-02T14:23:58.178+0000

• Duration: 12 min 56 sec

Test stats 🧪

Test	Results
Failed	0
Passed	25
Skipped	4
Total	29

[Mpdreamz]

Numbers without Zoom running:

Method	Mean	Error	StdDev	Median	Completed Work Items	Lock Contentions	Gen 0	Gen 1	Gen 2	Allocated
Empty	1.118 μs	0.0054 μs	0.0048 μs	1.117 μs	0.0000	-	0.1125	-	-	712 B
Minimal	1.815 μs	0.0122 μs	0.0114 μs	1.808 μs	0.0000	-	0.1450	-	-	928 B
Complex	4.807 μs	0.0345 μs	0.0306 μs	4.800 μs	0.0000	-	0.3357	-	-	2152 B
Full	482.182 μs	40.7989 μs	116.4016 μs	448.217 μs	-	-	-	-	-	41472 B