Add project introduction (#660) #1753

Job	Run time
check	1m 4s
fuzz record_ref	6m 39s
fuzz select_query	7m 48s
cross x86_64-unknown-linux-gnu (stable)	1m 50s
cross x86_64-unknown-linux-gnu (beta)	2m 8s
cross x86_64-unknown-linux-gnu (nightly)	1m 51s
cross x86_64-unknown-linux-musl (stable)	2m 9s
cross aarch64-unknown-linux-gnu (stable)	1m 53s
cross aarch64-unknown-linux-musl (stable)	2m 27s
test x86_64-unknown-linux-gnu (stable)	2m 9s
test x86_64-unknown-linux-gnu (beta)	2m 9s
test x86_64-unknown-linux-gnu (nightly)	2m 2s
test x86_64-apple-darwin (stable)	2m 50s
test x86_64-apple-darwin (beta)	3m 26s
test x86_64-apple-darwin (nightly)	3m 11s
test x86_64-pc-windows-gnu (stable)	3m 20s
test i686-pc-windows-msvc (stable)	3m 52s
fmt	20s
audit	56s
clippy	1m 6s
upgrades	2m 13s
book	4m 15s
deny	1m 31s
miri	2m 37s
gh-pages	4m 15s
	1h 8m 1s

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