(env/deps): use agilgur5/tsdx fork for esModuleInterop etc

- this uses my fork which merged my PR/commit that fixes the missing
  __esModule in CJS build output
  - which has been an issue in this library since adopting tsdx, as
    that's still an undocumented bug in tsdx
    - the bug means that default imports get transpiled to x = require
      instead of { default: x } = require
      - which affects anyone using CJS and importing the default export
        - and most apps still transpile down, as do most test runners,
          so basically it affects almost everyone using the default
    - for more details, see #12
  - until this fix is merged and released in the root library, will
    be using this fork

- it also has my recently merged PR/commit that changes the cacheRoot
  to ./node_modules/.cache/ instead of ./rts2_cache_* directories
  - can remove them from gitignore and they no longer clutter app root

.gitignore

@@ -1,9 +1,6 @@
 ### tsdx ###
 
 dist/
-.rts2_cache_cjs
-.rts2_cache_esm
-.rts2_cache_umd
 coverage/
 
 ### Node ###

package.json

@@ -43,7 +43,7 @@
     "@types/jest": "^24.0.23",
     "mobx": "^5.11.0",
     "mobx-state-tree": "^3.14.0",
-    "tsdx": "^0.11.0",
+    "tsdx": "github:agilgur5/tsdx#dist",
     "typescript": "^3.5.2"
   }
 }