Roll custom RTL positioning code into this repo

[joshlory]

https://github.com/code-dot-org/code-dot-org/blob/8ec4f3aafe97968dd18f8f318bb15a6c6b50a422/apps/src/StudioApp.js#L1183-L1192

    // Keep blocks static relative to the right edge in RTL mode
    if (this.isUsingBlockly() && Blockly.RTL) {
      if (this.lastWorkspaceWidth && (this.lastWorkspaceWidth !== workspaceWidth)) {
        var blockOffset = workspaceWidth - this.lastWorkspaceWidth;
        Blockly.mainBlockSpace.getTopBlocks().forEach(function (topBlock) {
          topBlock.moveBy(blockOffset, 0);
        });
      }
    }
    this.lastWorkspaceWidth = workspaceWidth;