Support reading query URL params

#### Is your feature request related to a problem? Please describe
Would like to pass key/var pairs into the app.

(A clear and concise description of what the problem is. Ex. I'm always frustrated when [...])

#### Describe the solution you'd like
Would like to pass URL query parameters into the app. For example: h20-wave-app-url?key1=var1,key2=var2, etc...

(A clear and concise description of what you want to happen.)

We could then read the vars in the app. Ex something similar to this: https://www.w3docs.com/snippets/php/get-url-query-string-parameters.html#:~:text=To%20get%20the%20query%20string,of%20the%20query%20string%20parameters.&text=Note%20that%20if%20the%20parameter,if%20a%20parameter%20is%20set.

#### Describe alternatives you've considered
The hash works to pass a string into the app however it must be delimited for multiple values and cannot be assigned keys. Ex. h2o-wave-app-url#somevariable,someothervariable, ...

(A clear and concise description of any alternative solutions or features you've considered.)

#### Additional context

Add any other context or screenshots about the feature request here.

Start by locating the app entry point and existing URL hash parsing, then inspect how values are passed into the app. Implement support for query-string key/value pairs while preserving the existing hash behavior, and add or update tests for multiple parameters and their availability to the app.

Written by the indexing model from the issue text.