Follow-up of #981 to fix restructuredText formatting and add the install instruction link to other plugins' READMEs as well which are similarly structured.

Closes https://github.com/geany/geany/issues/2508. You can view, comment on, or merge this pull request online at:

https://github.com/geany/geany-plugins/pull/1021

-- Commit Summary --

* Add link to how to install, fix some English * Docs: Add link to installation instructions to READMEs

-- File Changes --

M autoclose/README (4) M automark/README (3) M codenav/README (7) M defineformat/README (3) M geanypg/README (5) M lipsum/README (1) M pretty-printer/README (1) M shiftcolumn/README (1) M spellcheck/README (10) M updatechecker/README (1)

-- Patch Links --

https://github.com/geany/geany-plugins/pull/1021.patch https://github.com/geany/geany-plugins/pull/1021.diff