I just paraphrased the summaries from the sub-packages' Nuget Readmes and added them to the grid of packages in the Readme. Is that a good spot for them, and are those summaries sufficient? PR would close #1488 

Co-authored-by: NNick Craver <nrcraver@gmail.com>

As per https://docs.microsoft.com/en-us/dotnet/core/tools/sdk-errors/netsdk1174 `-p` is deprecated in favor of `--project`
This PR fixes the deprecation warning when running the benchmarks as currently described in the README.

Considering all of the inquiries on StackOverflow about DynamicParameters, there should probably be a simple overview in the documentation.
Examples:

- https://stackoverflow.com/questions/12723922/dapper-adddynamicparams-for-in-statement-with-dynamic-parameter-name
- https://stackoverflow.com/questions/43412455/dapper-with-sql-query-dynamic-parameters
- https://stackoverflow.com/questions/38443739/passing-dynamically-created-sql-parameters-into-dapper-as-an-anonymous-type
- https://stackoverflow.com/questions/62448900/how-do-i-loop-through-dapper-dynamic-query-results-using-strings-as-parameters
- https://stackoverflow.com/questions/36735189/dapper-dynamicparameters-returning-error

* snowflake tests #1687

* actually add the tests!

* merge

* context: #1716 https://github.com/DapperLib/Dapper/issues/1716

- change type-map to allow nullable
- change DateTime/TimeSpan to null
- do not specify DbType for null
- semi-breaking change: swap GetDbType to SetDbType, noting that it is marked [Obsolete] and internal-use-only
- semi-breaking change: make LookupDbType return nullable (same internal-use/[Obsolete])

* add test for Npgsql 6.0.0-rc.1

* try list parameters (like arrays)

* never assign -1 (sentinel) as the .DbType

* postgres tests

Fix verbiage for return type documentation comments.

Another example for "Execute a command Multiple Times" when we have an existing collection. The existing example (which still remains) I found to be a little bit confusing when I had an existing collection. So hopefully this 2nd example will help a tiny bit.

* snowflake tests #1687

* actually add the tests!

Add Documentation for Dapper.SqlBuilder (Issue #688, #480)

This address feedback in #1646

This merges in the work in #1663 and cleans up the convert a bit further.

Fixes #1538 and #1545 by making DbString.ToString() much more descriptive.

Fixes #866. This provides a more informative error, saying _which_ splitOn column couldn't be found in the result set.