docs: work with remote pinning services in webui

[lidel]

This PR updates docs/how-to/work-with-pinning-services.md to match webui v0.12.3 (shipped with go-ipfs v0.9.0)

Closes #820 and symbolically wraps up ipfs/ipfs-gui#91 📌 🤏

[jessicaschilling]

Can we please avoid these? It's duplication for people who are viewing this on docs.ipfs.io.

[lidel]

In this specific case toc here is useful, because it provides links to GUI and CLI sections, while the outline in the left menu does not:

Makes it way easier for people to jump to specific guide.

[johnnymatthews]

I moved the two new links in the [TOC] further down the page where they're relevant. Everything else looks good. Merge when ready :)

[filecorgi]

• Image optimization came back clean!
• Vuepress build was successful!

docs/how-to/work-with-pinning-services.md:

• The following link returned HTTP status code 301 (Moved Permanently):
  https://ipfs.github.io/pinning-services-api-spec
• The following link returned HTTP status code 301 (Moved Permanently):
  https://github.com/ipfs-shipyard/ipfs-webui
• Only proper nouns start with an uppercase character (there are exceptions for headlines).

  # Work with remote pinning services Depending on how you use IPFS, you might fi...
                                      ^^^^^^^^^
  

• Although a hyphen is possible, it is not necessary in a compound modifier in which the first word is an adverb that ends in ‘ly’.

  ...ne garbage collection that IPFS does on infrequently-used items in order to ...
                                             ^^^^^^^^^^^^^^^^^
  

• Consider a shorter alternative to avoid wordiness.

  ...at IPFS does on infrequently-used items in order to efficiently manage stora...
                                             ^^^^^^^^^^^
  

• ‘Pinata’ is an imported foreign expression, which originally has a diacritic. Consider using “piñata”

  ... important files, some of which include Pinata, Temporal, Crust, Infura, and...
                                             ^^^^^^
  

• ‘Pinata’ is an imported foreign expression, which originally has a diacritic. Consider using “piñata”

  ... pin remote --help. As of January 2021, Pinata  (opens new window) supports ...
                                             ^^^^^^
  

• The abbreviation “e.g.” (= for example) requires two periods.

  ...w other details: Preconfigured service (eg. Pinata) Custom service   A nickn...
                                             ^^^
  

• ‘Pinata’ is an imported foreign expression, which originally has a diacritic. Consider using “piñata”

  ...her details: Preconfigured service (eg. Pinata) Custom service   A nickname ...
                                             ^^^^^^
  

• Possibly missing article found.

  ...mentation for more info. To illustrate, example below shows which value shou...
                                             ^^^^^^^
  

• Possibly missing comma found.

  ...tation for more info. # Using a pinning service Here are a few CLI commands ...
                                             ^^^^^^^
  

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “your”.

  ...ore commands and general help: # Create your own pinning service Obviously y...
                                             ^^^^^^^^
  

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “your”.

  ...e for your friends or company. Starting your own commercial pinning service....
                                             ^^^^^^^^
  

• Consider a shorter alternative to avoid wordiness.

  ...Pinning Service API  (opens new window) in order to be interoperable with cl...
                                             ^^^^^^^^^^^
  

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “your”.

  ...s. TIP If you're interested in creating your own pinning service for your ow...
                                             ^^^^^^^^
  

• Use ‘own’ only if you want to emphasize that something belongs to a person or thing or was done by a person or thing. Consider writing “your”.

  ...n creating your own pinning service for your own personal or shared use, you...
                                             ^^^^^^^^
  

• Consider a shorter alternative to avoid wordiness.

  ... Web UI GitHub repo  (opens new window) in order to add it to the default li...
                                             ^^^^^^^^^^^