With this PR, when JS is activated and WASM supported, the article editor will be dynamically replaced with `contenteditable`s elements. This makes the editing interface simpler and less like a regular form. It will also allow us to easily add visual formatting with native browser APIs (and to insert images or videos directly). Here is a little demo:
There is still a lot to do, but it is a good first step.
Fixes#255
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
