Add instruction for completion

[willbasky]

This change is 

[cblp]

Reviewed 2 of 2 files at r1.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @willbasky)

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CHANGELOG.md, line 11 at r1 (raw file):

- Track issue content
- Add wiki notes
- Add completion instruction

Add completion installation instruction

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README.md, line 33 at r1 (raw file):

### Completion for commands and options (tested on Ubuntu 18.04)

    ff --bash-completion-script `which ff` | sudo tee /etc/bash_completion.d/ff

Добавь "MacOS with brew" — каталог /usr/local/etc/bash_completion.d/

[willbasky]

Добавь "MacOS with brew" — каталог /usr/local/etc/bash_completion.d/

ff --bash-completion-script which ff | sudo tee /usr/local/etc/bash_completion.d/ff

??

[cblp]

Reviewed 2 of 2 files at r2.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @willbasky)

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README.md, line 39 at r2 (raw file):

#### MacOS

    ff --bash-completion-script which ff | sudo tee /usr/local/etc/bash_completion.d/ff

кавычки пропустил

[cblp]

Reviewed 1 of 3 files at r3.
Reviewable status: 2 of 4 files reviewed, all discussions resolved

[cblp]

Reviewable status: complete! all files reviewed, all discussions resolved