message: docs(building-for-ibm): updated headings to follow style convention
  ### Related Ticket(s)
  No related issue
  ### Description
  This updates the headings in `Building for IBM.com` to follow style conventions.
  ### Changelog
  **Changed**
  `building-for-ibm-dotcom.md`
diff: - [Overview](#overview)
  - [Digital data object](#digital-data-object)
  -- [Page Language](#page-language)
  +- [Page language](#page-language)
  - [Configuring available languages](#configuring-available-languages)
  -- [Meta Tags](#meta-tags)
  -- [IBM.com Tag Management and Site Analytics](#ibmcom-tag-management-and-site-analytics)
  +- [Meta tags](#meta-tags)
  +- [IBM.com tag management and site analytics](#ibmcom-tag-management-and-site-analytics)
  <!-- END doctoc generated TOC please keep comment here to allow auto update -->
  <!-- prettier-ignore-end -->
  @@ -72,7 +72,7 @@ for your page:
  </script>
  ```
  -## Page Language
  +## Page language
  The page language is a requirement in order to define what language the current
  page is translated in.
  @@ -143,7 +143,7 @@ For example:
  ```
  -## Meta Tags
  +## Meta tags
  These meta tags are required for all IBM.com pages:
  @@ -158,7 +158,7 @@ These meta tags are required for all IBM.com pages:
  <meta name="robots" content="index,follow">
  ```
  -## IBM.com Tag Management and Site Analytics
  +## IBM.com tag management and site analytics
  It is required to include the common script tag that allows tag management and
  site analytics on all IBM.com pages. The following must be included on every
  