Feat: Add live translation for hotzone tab

[KHwong12]

Summary

This branch adds live language translation for hotzone tab.

https://user-images.githubusercontent.com/29334677/188651073-8fa86d29-616a-4cf4-ba61-32834ac34c03.mp4

Changes

The changes made in this PR are:

1. Add two new columns, Name_zh and District_zh in the raw spatial data of hotzone street sections (hotzone_streets.gpkg) and table (hotzone_out_df.fst)
2. Add live language translation to the interactive hotzone map, including 1. legend name, 2. layer name and 3. popup details.
3. Add live language translation to the details of interactive table (datatable), including column names and attributes.
4. Add live language translation to the interactive table (datatable) UI.

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Check

• [ ] (If UI & data are updated) The UI & data includes Traditional Chinese translation, with translation terms wrapped in i18n$t() and terms added to translation_zh.csv
• [ ] The travis.ci and R CMD checks pass.

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Note

The current approach for live translation that cannot be done by simply using i18n$t() (#73) is to wrap variables into a if(input$selected_language == "en") {} else {} control flow.

if(input$selected_language == "en") {TABLE_COLUMN_NAMES_EN} else {TABLE_COLUMN_NAMES_ZH}