Cleaned en.json with checking scripts

[yuanwang04]

fix #328

Wrote scripts to check for missing keys and extra keys in en.json and es.json. It will automatically remove extra keys.

For this script to work, keys in en.json and es.json should only include [a-zA-Z0-9-_]. Especially it should NOT include '.'

The script is based on jest. To run, use npm run test.

A cleaned version of en.json/es.json will be created in locales/newEn.json and locales/newEs.json

The following keys seem to be missing in es.json:
[
"missing_locations.title",
"missing_locations.description",
"missing_locations.import_button",
"disclaimer.title",
"disclaimer.content",
"location.unknown",
"data_storage_modal.title",
"data_storage_modal.desc_1",
"data_storage_modal.desc_2",
"data_storage_modal.delete_success",
"data_storage_modal.delete_failure",
"data_storage_modal.delete_button",
"export.message",
"export.title",
"export.description"
]

[cheng-tan]

Can we only have three test cases in this file and break down this PR:

1. There is no unused keys (only check the en.json file, make sure all the keys is used in the app)
2. There is no missing keys (all the keys used in the app are having values in en.json)
3. Every language has same keys (Load in all translations file and check if their keys are the same)