docs: Update urls to use https

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

docs/build-instructions.md

@@ -24,14 +24,14 @@ To get the source files:
 
 ### Native Builds
 
-*Ping-Viewer* builds are supported for Windows, Linux and macOS. This is possible with the [Qt toolkit](http://www.qt.io) as its cross-platform support library.
+*Ping-Viewer* builds are supported for Windows, Linux and macOS. This is possible with the [Qt toolkit](https://www.qt.io) as its cross-platform support library.
 
 - **macOS:** v10.14 or higher
 - **Linux:** 64 bit, gcc-8 or clang-7 compiler versions or higher
 - **Windows:** 10 or higher, Visual Studio 2017 compiler (64 bit)
 - **Qt version:** 5.15 **(only)**
 
-> **Tip:** For more information see: [Qt 5 supported platform list](http://doc.qt.io/qt-5/supported-platforms.html).
+> **Tip:** For more information see: [Qt 5 supported platform list](https://doc.qt.io/qt-5/supported-platforms.html).
 
 #### Install Visual Studio 2017 (Windows Only)
 
@@ -41,7 +41,7 @@ When installing, you must minimally select all Visual C++ components.
 
 #### Install Qt
 
-1. Download and run the [Qt Online Installer](http://www.qt.io/download-open-source).
+1. Download and run the [Qt Online Installer](https://www.qt.io/download-open-source).
 2. In the installer *Select Components* dialog choose: 5.15.
 
    Then install just the following components:

docs/device-settings-ping360.md

@@ -12,6 +12,6 @@
 > Click the arrow on the Device Settings menu to access these advanced settings
 
 - **Transmit Duration:** The length of time to transmit for in each ping. Longer durations send more sound energy, so are more likely to get a response, but come at the cost of range precision for the responses. Updates to the range setting automatically update this to maximise response strength for the current range resolution. In enclosed or otherwise acoustically noisy environments it can help to reduce this and the receiver gain, and in open water with far away and/or small targets it can help to increase them.
-- **Transmit Frequency:** Changes the frequency of the emitted pulse. [Lower frequencies are less absorbed by water](http://resource.npl.co.uk/acoustics/techguides/seaabsorption/physics.html), but the Ping360 transducer is tuned to 750kHz and less sensitive to other frequencies. Practically recommended to stay within 650-850kHz. Can make minor changes to account for the doppler effect if consistently moving quickly (e.g. if moving at 1.5m/s (BlueROV2 max forward speed) reduce by 1-3kHz to optimise receiver sensitivity to objects being approached). May be useful for reducing interference to other nearby sensors with a similar acoustic range sensitivity.
+- **Transmit Frequency:** Changes the frequency of the emitted pulse. [Lower frequencies are less absorbed by water](https://resource.npl.co.uk/acoustics/techguides/seaabsorption/physics.html), but the Ping360 transducer is tuned to 750kHz and less sensitive to other frequencies. Practically recommended to stay within 650-850kHz. Can make minor changes to account for the doppler effect if consistently moving quickly (e.g. if moving at 1.5m/s (BlueROV2 max forward speed) reduce by 1-3kHz to optimise receiver sensitivity to objects being approached). May be useful for reducing interference to other nearby sensors with a similar acoustic range sensitivity.
 - **Speed of Sound:** The speed of sound to be used for distance calculations. At 20℃ this should be roughly 1520 m/s in salt water, 1480 m/s in fresh water (It's not possible to use Ping360 in air!). See [this calculator](https://bluerobotics.com/learn/speed-of-sound-in-water-calculator) for more accurate speeds in water at different depths, temperatures, and salinity levels.
 - **Angular Resolution:** Changes the step between each sample. Enables scanning a sector faster at the expense of a lower angular resolution.

docs/display-settings.md

@@ -59,7 +59,7 @@ The user can create his own gradients for the waterfall, for this, it's necessar
     4. `#RRRGGGBBB`
     5. `#RRRRGGGGBBBB`
 
-    There is a very good tool to help with gradient colours [here](http://www.perbang.dk/rgbgradient/).
+    There is a very good tool to help with gradient colours [here](https://www.perbang.dk/rgbgradient/).
 
 6. First value will represent 0.0
 7. The last value will represent 1.0

docs/firmware-update.md

@@ -87,7 +87,7 @@ You should see the following output:
 ```
 stm32flash 0.5
 
-http://stm32flash.sourceforge.net/
+https://stm32flash.sourceforge.net/
 
 Using Parser : Intel HEX
 Interface serial_posix: 115200 8E1