v1.21.15

Fix filename related edge cases

This release fixes some filename related edge cases:

* Prepend `filename.sort_tag_extra_separator` in case the note's title
  field is empty.
* Append `filename.copy_counter_extra_separator` in case the file stem
  resembles a copy counter.

v1.21.14

Fix a minor regression when the title contains only sort-tag characters

This release fixes a minor regression introduced with Tp-Note v1.21.10: Note
files, created with title fields containing only sort tag characters, need an
`extra_separator` between in the sort-tag and the title in their filename.
Failing this rule caused cyclic filename change when synchronizing the note's
metadata and the filename. Now, an extra-separator is correctly inserted
as before.

v1.21.9

Maintenance release, no new features

* Docs updated
* `atty` crate dependency removed

v1.21.8

Windows: default file extension is `.md`

Recent versions of `notepad` can deal with `.md` files. From this release on,
all created note files on all platforms have `.md` extension.

Configuration file: the variables `app_args.*` interpret
`{{ get_env(name="<ENVIRONMENT_VARIABLE>") }}` as templates variable.

v1.21.7

Maintenance release: improve the natural language detection speed

Maintenance release:

* Improve the natural language detection speed
* Reduce the binary size by 20%
* Improve the test harnesses

v1.21.6

Add compilation feature `lang-detection`

v1.21.5

Rename the root dir marker `.tpnoteroot`; Add pseudo lang. tag `+all`

* Breaking change: rename root directory marker file from `.tpnoteroot` to
  `.tpnote.toml`.

* Allow optional project specific configuration data in `.tpnote.toml`.
  Tp-Note will source the configuration for all note file in all subdirectories.
  Empty `.tpnote.toml` content is still allowed.

* Interpret the pseudo language tag `+all` in the environment variable
  `TPNOTE_LANG_DETECTION` and the configuration file variable
  `tmpl.filter_get_lang` as "select all available languages".

v1.21.4

Maintenance release

To improve the template readability the following template filters have
been renamed:

* `ext` to `file_ext`
* `stem` to `file_stem`
* `tag` to `file_sort_tag`
* `trim_tag` to `trim_file_sort_tag`
* `copy_counter` to `file_copy_counter`

The new environment variable `TPNOTE_EXTENSION_DEFAULT` allows setting the
file extension of new note files. If set, it overwrites the
`filename.extension_default` configuration file variable.

v1.21.3

Link docs with new sort-tag shorthand link syntax

• Hyperlinks to other Tp-Note documents can now be shortened by referencing
  only the target's sort-tag, e.g. [my doc](<home/20230510-my note.md>) is
  equivalent to [my doc](<home/20230510>). Autolinks can be shortened as
  well: <http:home/20230510-my note.md> becomes <http:home/20230510>

• New environment variable: TPNOTE_CONFIG

• The prepend_dot filter is replaced by the prepend filter.
  The concerned filename templates have been updated.

Full Changelog: v1.21.2...v1.21.3

v1.21.2

Add `TPNOTE_EDITOR_CONSOLE` and `TPNOTE_LANG_DETECTION` environment v…