Problem: Currently, getting response timeout immediately results in
fail, it's desired to have a possibility to configure retries on
timeouts.
Solution: The new ExternalHttpTimeout error is added, which is treated
in a similar way as the ExternalHttpTooManyRequests error.
A new field is added to the config meaning how many timeouts are
allowed. Default value equals to 1.
Problem: bats tests are not space sensetive
Solution: remove trailing spaces from xrefcheck output
(see next problems), remove `--ignore-trailing-space`
from `assert_diff`
Problem: there are lines containing only spaces in
xrefcheck's output, because `Fmt.indentF` "indents"
empty lines too.
Solution: add `Xrefcheck.Util.Interpolate.interpolateIndentF`
function that is not indenting empty lines.
Same for `Fmt.blockListF` and `Fmt.blockListF'`.
Those functions are not adding trailing newlines, so it's
easier to use it in interpolation blocks.
Problem: when there is a current file link `[a](#b)`, it is
printed like
```
- text: "a"
- link: (trailing space here)
- anchor: b
```
Solution: like with anchors, print `link: -` instead
Problem: users need to manually disable ANSI coloring when their terminal
is not supporting it. Also we need to explicitly disable colors
if we want to redirect output in file during test
Solution: use `System.Console.Pretty.supportsPretty`
to detect if our terminal is not supporting colors
Problem: we had a lot redundant dependencies and had no linter for handling obvious errors
Solution: hlint support and enable -Weverything flag, fix all hints from them, add hlint to the CI pipeline
