message: Fix broken internal-links
  The Table of Contents section on i18n Contribution Guide page has many
  broken links. This commit will fix those broken internal-links.
diff: ## Table of Contents
  -- [Adding a new locale](#usage)
  +- [Adding a new locale](#adding-a-new-locale)
  - [Choosing a directory name for a locale](#choosing-a-directory-name-for-a-locale)
  - - [index.js](#indexjs)
  + - [index.js](#index.js)
  - [localize](#localize)
  - - [localize.ordinalNumber](#localizeordinalnumber)
  + - [localize.ordinalNumber](#localize.ordinalnumber)
  - - [localize.era and using buildLocalizeFn function](#localizeera-and-using-buildlocalizefn-function)
  + - [localize.era and using buildLocalizeFn function](#localize.era-and-using-buildlocalizefn-function)
  - [Formatting localizers](#formatting-localizers)
  - - [localize.quarter](#localizequarter)
  + - [localize.quarter](#localize.quarter)
  - - [localize.month](#localizemonth)
  + - [localize.month](#localize.month)
  - - [localize.day](#localizeday)
  + - [localize.day](#localize.day)
  - - [localize.dayPeriod](#localizedayperiod)
  + - [localize.dayPeriod](#localize.dayperiod)
  - [formatLong](#formatlong)
  - - [formatLong.dateFormats](#formatlongdateformats)
  + - [formatLong.dateFormats](#formatlong.dateformats)
  - - [formatLong.timeFormats](#formatlongtimeformats)
  + - [formatLong.timeFormats](#formatlong.timeformats)
  - - [formatLong.dateTimeFormats](#formatlongdatetimeformats)
  + - [formatLong.dateTimeFormats](#formatlong.datetimeformats)
  - [formatRelative](#formatrelative)
  