Rust can compile to WASM, so let's use it for front-end code as well.
To compile the front-end:
```
cargo install cargo-web
cargo web deploy -p plume-front
```
All the template are now compiled at compile-time with the `ructe` crate.
I preferred to use it instead of askama because it allows more complex Rust expressions, where askama only supports a small subset of expressions and doesn't allow them everywhere (for instance, `{{ macro!() | filter }}` would result in a parsing error).
The diff is quite huge, but there is normally no changes in functionality.
Fixes#161 and unblocks #110 and #273
Add migration to fix typo
Add support for linking hashtags with posts
Rework tag search page so it says a nicer message than page not found
when no post use that tag
Add new string to translation
For now it might be enough to only reword 'reshare' to 'boost' in the
frontend. The code can continue to use 'reshare'.
Includes the most recent German translation.
Fixes#74
