housekeeping: bundle size reductions (#4713)

* set new bundlesize goal
* preserve `GeneratorFunction` instead of all function names
* use js-yaml fork that doesn't require esprima
* set HTML content directly, instead of using React-Markdown
* use remarkable for all Markdown rendering
* add babel-plugin-transform-react-remove-prop-types
* remove SplitPaneMode plugin
* remove react-collapse
* remove AST plugin, and yaml-js
* trim Markdown HTML string output before rendering
* disable obsolete function name preservation
* add `getComponent` to propTypes

src/core/plugins/spec/actions.js

@@ -1,4 +1,4 @@
-import YAML from "js-yaml"
+import YAML from "@kyleshockey/js-yaml"
 import { Map } from "immutable"
 import parseUrl from "url-parse"
 import serializeError from "serialize-error"
@@ -80,7 +80,7 @@ export const parseToJson = (str) => ({specActions, specSelectors, errActions}) =
 
 let hasWarnedAboutResolveSpecDeprecation = false
 
-export const resolveSpec = (json, url) => ({specActions, specSelectors, errActions, fn: { fetch, resolve, AST }, getConfigs}) => {
+export const resolveSpec = (json, url) => ({specActions, specSelectors, errActions, fn: { fetch, resolve, AST = {} }, getConfigs}) => {
   if(!hasWarnedAboutResolveSpecDeprecation) {
     console.warn(`specActions.resolveSpec is deprecated since v3.10.0 and will be removed in v4.0.0; use requestResolvedSubtree instead!`)
     hasWarnedAboutResolveSpecDeprecation = true
@@ -100,7 +100,7 @@ export const resolveSpec = (json, url) => ({specActions, specSelectors, errActio
     url = specSelectors.url()
   }
 
-  let { getLineNumberForPath } = AST
+  let getLineNumberForPath = AST.getLineNumberForPath ? AST.getLineNumberForPath : () => undefined
 
   let specStr = specSelectors.specStr()
 
@@ -149,7 +149,7 @@ const debResolveSubtrees = debounce(async () => {
       errSelectors,
       fn: {
         resolveSubtree,
-        AST: { getLineNumberForPath }
+        AST = {}
       },
       specSelectors,
       specActions,
@@ -160,6 +160,8 @@ const debResolveSubtrees = debounce(async () => {
     return
   }
 
+  let getLineNumberForPath = AST.getLineNumberForPath ? AST.getLineNumberForPath : () => undefined
+
   const specStr = specSelectors.specStr()
 
   const {