Update wording on dashboard page

To encourage users to feel like a part of sr.ht
Allow paste slugs to break

Ref: ~sircmpwn/sr.ht#245
.builds/alpine.yml: increase specificity of sed
Add search by filename/visibility/sha to /~u

Ref: ~sircmpwn/paste.sr.ht#5
add database stamp for core.sr.ht
Replace misaka (hoedown) with mistletoe

It looked like using hoedown (through misaka), which is very
unmaintained, was leading to a lot of issues (see [0]). This replaces
misaka by mistletoe [1], without losing any functionality (I hope).

This affects the call to 'markdown()', removing the now-redundant
argument for the tag whitelist.

[0]: https://todo.sr.ht/~sircmpwn/sr.ht/20
[1]: https://github.com/miyuchina/mistletoe
Alpine: upgrade to 3.12
pastesrht-initdb: import webhooks
setup.py: use importlib.resources from python 3.7 to find core.sr.ht Makefile

importlib.resources will guarantee to find any importable module, and
check that the resource ('Makefile') can be found within it.

This lets us get rid of the current getsitepackages() hack and
environment variable fallback, which is both verbose and badly handles
some edge cases when installing modules, and instead use the recommended
way to find data files shipped with a python module.
Add pastesrht-initdb
Responsiveness improvements
7c883560 — George Craggs 10 months ago 0.10.1
Flush paste after validation

Flush paste after the validation has taken place to prevent 404's after
an invalid submission.

Add <title> to paste pages
Add new and move existing paste visibility indicators
Update Makefile to use python 3.8
alpine.yml: switch to alpine 3.11
Improve config.example.ini
Add user information to profile pages

Change user profile pages to display the user's bio, URL, location, etc.
as per other sr.ht services. (Previously, all user pages displayed the
"Welcome back, username!" text from the front page.)

Signed-off-by: Benjamin Lowry <ben@ben.gmbh>
public.py: Fix None dereference
Add a build manifest for Debian packaging
Updates for single-sign-on support