Utilizes ModalBase to lock scroll on mobile filters

[dzucconi]

Unexciting :) most of the nice things in the ModalBase like the focus management would apply more to desktop uses but this at least does a better job of locking the scrolling on mobile.

Also snuck in tapping on filter to scroll to top since that's expected from a UX perspective but wouldn't work due to the modal context.

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[dzucconi]

Just realizing that button for "Filter" will look a bit weird on Desktop if this view ever happens to be triggered there. We really need an un-styled button primitive in palette — like the equivalent of TouchableWithoutFeedback. I'll PR one.

[ArtsyOpenSource]

	Fails
🚫	Danger failed to run dangerfile.ts.

Error RangeError

Maximum call stack size exceeded
RangeError: Maximum call stack size exceeded
    at Object.parsePropertyName (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:2438:23)
    at Object.parseObjectMember (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:9291:10)
    at Object.parseObj (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:9225:25)
    at Object.parseExprAtom (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:8855:28)
    at Object.parseExprAtom (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:3609:20)
    at Object.parseExprSubscripts (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:8483:23)
    at Object.parseMaybeUnary (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:8463:21)
    at Object.parseExprOps (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:8329:23)
    at Object.parseMaybeConditional (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:8302:23)
    at Object.parseMaybeAssign (/home/circleci/project/node_modules/@babel/core/node_modules/@babel/parser/lib/index.js:8249:21)

Dangerfile

---------------------------^

Generated by 🚫 dangerJS against 7337b41

[anandaroop]

Whoa, ModalBase looks handy 😄

[anandaroop]

LGTM save for the odd little snapshot failure in CI